THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 

IN  MEMORY  OF 

Dr. Harold  «.   Fairbanks 


PRESENTED  BY 

Miss  Helen  K.   Fairbanks 


The  RALPH  P.,  REED  LIBRARY 

DEPARTMENT  OF  GEOLOGY 

UNIVERSITY  of  CALIFORNIA 
L08  ANGELES,  CALIF. 


"•£- 


SYLLABUS 


A   COURSE   OF   LECTURES 


ELEMENTARY    GEOLOGY 


JOHN    C.  BRANNER,  PH.  D. 

Professor  of  Geology  in  Leland  Stanford  Junior  University 


Second  Edition 


STANFORD  UNIVERSITY 
1902 


STANFORD  UNIVERSITY  PRESS 


Library 


CONTENTS. 


PAGE 

TEXT-BOOKS  OF  GEOLOGY 4 

THE  DATA  OP  GEOLOGY  6-8 

PART  I. 
DYNAMIC  GEOLOGY,  OR  ROCK-MAKING  AGENCIES     ....      10-210 

PART  II. 
STRUCTURAL  GEOLOGY,  OR  THE  MODIFICATIONS  OF  ROCKS       .        .     212-288 

PART  III. 

HISTORICAL  GEOLOGY,  OR  PALEONTOLOGY.     THE  ORDER  OF  EVENTS 

AND  LIFE  AS  RECORDED  IN  THE  ROCKS          ....     290-326 

PART  IV. 

PHYSIOGRAPHY,  OR  TOPOGRAPHIC  GEOLOGY.      THE  SURFACE   FEAT- 
URES OF  THE  EARTH 328-356 

INDEX .     362-369 


775680 


INTRODUCTION. 


The  method  of  presentation  followed  in  these  lectures  is  not  intended 
to  be  a  strictly  logical  one  from  a  geological  point  of  view.  It  is  not  thought 
that  the  logic  of  the  subject  as  a  whole  is  of  any  particular  importance  to 
the  student  until  he  shall  have  gained  a  good  general  knowledge  of  geologi- 
cal phenomena  and  of  geological  principles. 

It  is  the  aim  to  begin  with  those  phenomena  with  which  the  average 
student  is  most  likely  to  be  familiar,  and  by  using  this  familiarity  to  branch 
out  so  as  to  cover  the  whole  field,  in  so  far  as  it  can  be  done  in  such  an 
elementary  course  of  lectures. 

The  order  of  presentation  is  approximately  that  followed  in  the  text- 
books. 

The  student  cannot  be  too  deeply  impressed  with  the  fact  that,  if  he  is 
to  get  a  real  knowledge  of  geology,  he  must  go  out  of  doors  and  see  it  face 
to  face.  No  amount  of  book  study,  however  important  and  thorough  it 
may  be,  can  take  the  place  of  this  field  study.  But  neither  must  books  be 
neglected,  for  they  contain  the  results  of  what  others  have  seen  and 
thought. 

The  foot-note  references  will  enable  students  to  extend  their  knowledge 
by  reading.  These  references  are  not  intended  to  be  full,  but  the  papers 
cited  almost  invariably  mention  others  upon  the  same  subject,  and  some 
of  them  contain  full  bibliographies. 


TEXT-BOOKS  OF  GEOLOGY. 

MANUAL  OF  GEOLOGY.     By  James  D.  Dana.    Fourth  edition,  New  York, 

1895.     1087  pages.     Price,  $5.00. 
AN  INTRODUCTION  TO  GEOLOGY.  By  W.  B.  Scott.  New  York,  1897.  573-(-xxvii 

pages.    Price,  $1.90. 

TEXT-BOOK  OP  GEOLOGY.     By  Sir  Archibald  Geikie.     Third  edition,  Lon- 
don and  New  York,  1893.     1147+xvii  pages.     Price,  $7.50. 
PHYSICAL  GEOLOGY.     By  A.  H.  Green.     London,  1882.     728-4-xxiv  pages. 

Price,  $6.00. 
GEOLOGY,  CHEMICAL,  PHYSICAL,  AND   STRATIGRAPHICAL.     By  Joseph   Prest- 

wich.     Oxford,  1886.     2  vols.,  1083+lii  pages.     Price,  $15.00. 
PRINCIPLES  OF  GEOLOGY.     By  Sir  Charles  Lyell.     Eleventh  edition,  2  vols., 

New  York,  1889.     1323+xxxix  pages.     Price,  $8.00. 
TKAITE   DE  GEOLOGIE.     Par  A.  de   Lapparent.     2me  edition,  Paris,   1885. 

1504+xv  pages.    4me  edition,  Paris,  1900.    3  vols.,  1912+xxiii  pages. 

Price,  $10.00.    . 
TH*:  STUDENT'S  HAND-BOOK  OF  PHYSICAL  GEOLOGY.     By  A.  J.  Jukes-Browne. 

London,  1884.    514+xii  pages.     Price,  $2.40.     New  edition,  London, 

1902. 
ELEMENTE  DER  GEOLOGIE.     Von   Dr.    Hermann    Credner.     Leipzig,  1887. 

808+xx  pages.     Price,  $6.00. 
ELEMENTS  OF  GEOLOGY.     By  Joseph  Le  Conte.     New  York,  1896.    640+xvii 

pages.     Price,  $4.00. 
REVISED  TEXT- BOOK  OF  GEOLOGY.    By  James  D.  Dana.    Fifth  edition,  edited 

by  Wm.  North  Rice.    New  York  [1898].     Price,  $1.40. 
A  TEXT-BOOK  OF  GEOLOGY.     By  A.  P.  Brigham.     New  York,  1901.     Price, 

,*1.50. 


ELEMENTARY    GEOLOGY. 


THE  DATA  OP  GEOLOGY. 

Geology  has  to  do  with  the  structure  and  history  of  the  earth. 

Geologic  reasoning  is  based  on  the  supposition  that  the  operation  of 
geologic  agencies  is  constant  under  given  conditions. 

Geology  deals  with  two  classes  of  phenomena : 

I.  OBJECTIVE  PHENOMENA,  or  the  materials,  structure,  and  forms  of  the 
earth.     These  phenomena  are : 

1.  Rocks  and  their  constituents. 

The  earth  is  made  of  rocks. 
Geologic  definition  of  rocks. 
The  rocks  are  made  of  minerals. 
Examples  of  different  kinds  of  rocks: 

Conglomerates,   pebbles,   pudding-stones,   sands,  sandstones, 
clays,  shales. 

Igneous  rocks. 

2.  Structural  features,  or  the  internal  conditions  and  changes  of  the 

rocks. 

What  is  meant  by  the  earth's  structure. 

Examples  exposed  in  canons,  gorges,  gullies,  road  and   railway 
cuts,  mines,  tunnels,  and  wells. 


Fig.  1.— Vertical  section  in  the  Ozark  mountains  of  Arkansas,  showing  horizontal,  bent, 
and  broken  layers  of  rocks. 

3.  Topographic  forms,  or  external  changes  of  rocks. 

What  is  meant  by  topography  or  physiography,  or  the  external 

modifications  of  rocks. 
Examples  of  various  types  of  topography  and  the  relations  of  these 

forms  to  geology. 


8 


DATA  OF  GEOLOGY. 


In  order  to  understand  the  forms,  we  must  understand  the  structure ; 
to  understand  the  structure,  we  must  understand  how  the  rocks  are  made 
and  modified. 

That  branch  of  geology  which  deals  with  the  topographic  forms  and 
surface  features  of  the  earth,  their  origin  and  modification,  is  called  Topo- 
graphic Geology,  or  Physiography.  It  will  be  treated  of  in  Part  IV. 


Fig.  2  —Example  of  parallel  ridges  and  valleys  due  to  folding  and  denudation  of 
alternate  hard  and  soft  layers  of  rock.    (Means.) 

II.  SUBJECTIVE  PHENOMENA,  or  the  processes  by  which  those  materials  of 
which  the  earth  is  formed  have  reached  their  present  conditions. 

The  agencies  and  processes  of  rock-making  are  called  DYNAMICAL  GEOL- 
OGY, and  are  discussed  in  Part  I. 

The  earth's  history  as  preserved  in  rocks  is  but  fragmental  at  best. 
These  fragments  are  contained  in  the  materials,  structure,  and  forms  of 
the  earth. 

The  rock  records  are  not  everywhere  the  same,  nor  everywhere  equally 
accessible,  while  enormous  portions  of  them  have  been  obscured,  or  en- 
tirely wiped  out  by  the  changes  of  time. 


10 


PART   I. 


DYNAMICAL  GEOLOGY. 

Dynamical  geology  is  that  branch  which  deals  with  rock-making  and 
rock-destroying  agencies.  Rocks  may  be  classed  as  — 

1.  Mechanical  sediments,  or  rocks  deposited  mechanically,  either  by  air 

or  by  water.     They  are  usually  called  sedimentary  rocks. 

2.  Chemical  deposits,  or  precipitates  from  solution  in  gases  or  in  water. 

3.  Igneous  rocks,  or  those  cooled  and  hardened  from  a  fused  condi- 

tion. 

4.  Rocks  of  organic  origin,  or  those  made  by  accumulations  of  organic 

matter. 

These  embrace  all  the  kinds  of  rocks  in  all  parts  of  the  globe. 

All  rocks  have  peculiarities  or  characteristics  due  to  the  methods  of 
their  formation.  It  is,  therefore,  necessary  to  understand  these  methods 
or  agencies,  in  order  to  know  how  and  under  what  circumstances  the  rocks 
were  formed. 


GEOLOGIC  AGENCIES. 

Geologic  agencies  are  those  that  either  make  or  destroy  the  rocks. 
They  may  be  grouped,  like  the  rocks  themselves,  as  follows : 


Agencies  -< 


( Atmospheric 
Mechanical    •< 

( Aqueous 

I  Solution 
Chemical        •< 
Igneous  (Precipitation 

(high  temperature) 

Organic 


( Direct 
(indirect 


11 


12  ATMOSPHERIC    AGENCIES. 


THE  DIRECT  WORK  OF  THE  ATMOSPHERE.* 

The  work  of  the  atmosphere  is  called  seolian,  and  the  deposits  are 
known  as  aeolian  rocks. 

The  direct  geologic  work  of  the  atmosphere  in  done  chiefly  in  arid 
regions  and  on  sandy  shores.  It  consists  of  carrying,  wearing,  and  deposit- 
ing. 

I.  The  Carrying  Done  by  the  Wind. 

Distribution  of  volcanic  dust  or  cinders. 

For  miles  around  Mount  Shasta;  Vesuvius;  wide-spread  tuff  beds  of 

Arizona. 

In  Iceland  ;t  in  South  America. i 
In  August,  1883,  eruption  of  Krakatoa,  in  Straits  of  Sunda;  ashes  fell 

nearly  1,000  miles  southwest  of  there. (> 
Skies  made  red  all  over  the  world,  till  November  of  that  year,  by  the 

fine  dust, H  which  rose  to  an  elevation  of  85,217  feet  in  Venezuela, 

and  106,250  feet  at  St.  Helena. 
Dust-  and  sand-storms  If  are  common  in  arid  regions,  but  they  also  occur  in 

regions  that  are  not  arid.** 
Burying  of  roads  and  railway  tracks. 
Filling  of  railway  cuts;  wind-breaks. 
Burial  of  forest  on  the  shores  of  Lake  Michigan. 
Burial  of  farms  of  west  Portugal ;  Bermuda. tt 
In  Asia  and  Africa  towns  and  cities  have  been  buried,  ii 
Sphinx  of  Egypt  half  buried  in  sand;  some  oases  being  buried. 
In  the  arid  parts  of  the  United  States  seolian  deposits  are  sometimes 

2,000  feet  thick. §§ 
Stamp-mill  buried  by  sand  on  desert  one  hundred  and  twenty  miles 

east  of  San  Bernardino,  California,  1896.     Church  buried. |||| 

*  Earth  sculpture.  By  James  Geikie.  Chap,  xii :  Land-forms  modified  by  asolian 
action,  250-265.  New  York.  1898. 

t  Across  the  Vatna  Jokull,  or  scenes  in  Iceland.  By  W.  L.  Watts.  105-108  160.  London, 
1876. 

J  Travels  amongst  the  Great  Andes  of  the  equator.  By  Edward  Whymper  125,  141, 
326,  328.  New  York,  1892. 

I  Nature,  April  24,  1884,  XXIX,  595. 

|  Nature,  December  6,  1883,  XXIX,  130-133.  -  Krakatoa  Com.  Rep.,  375. 

\  Dust-falls  and  their  origins.     Nature.  May  S,  1902,  p.  41. 

"Observations  on  dirt  storms.  By  E.  O.  Hershey.  Am.  Geol.,  June  1899,  XXIII, 
38M-382 

tt  The  Atlantic.    By  Wyville  Thomson.    Vol.  I,  291  et  seq. 

it  Logons  de  geologic  pratique.    Par  E.  de  Beaumont.    I,  193-194.    Paris,  1845. 

In  Palestine,  see  Mount  Seir,  Sinai  and  Western  Palestine.  By  E  Hull.  145-146.  Lon- 
don, 1889. 

n  I.  C.  Russell,  Geol   Mag.,  1889,  pp.  289,  342. 

III!  See  cases  cited  in  Woodward's  Geology  of  England  and  Wales,  2d  ed.,  546-547. 
London,  1H87. 


14  ATMOSPHERIC    AGENCIES. 

In  the  Argentine  Republic  dust  produces  darkness   and  obliterates 
landmarks  and  roads.* 

Darkness  caused  by  mineral  matter  in  the  air.t 

Estimated  that  such  storms  carry  at  least  2,000  tons  to  the  cubic  mile.t 

In  April,  1863,  several  inches  of  dust  fell  at  Peking,  China;  it  came 
from  the  cultivated  fields  of  Asia.§ 

In  February,  1898,  worn  sand,  probably  from  Sahara,  fell  on  shipboard 

nine  hundred  miles  off  the  coast  of  Africa.  || 
Distribution  of  plants  by  seeds  blown  over  the  earth,  if 

Seeds  with  wings,  etc.     "  Tumbleweed." 

Russian  thistle.** 

Diatoms. 
Distribution  of  animals. 

Birds,  blown  out  to  sea. 

Spiders,  locusts,  butterflies. 

Origin  of  insular  floras  and  faunas.  ft 

Influence  of  plants  and  animals  upon  geology. 

II.  The  Wearing  Done  by  Wind. 

Wind  alone  does  not  wear  rocks;  it  wears  with  what  it  carries.  tt 
Effect  of  the  impact  of  single  particles. 

Dulling  of  car  windows  in  arid  regions. 

Wearing  through  of  glass  panes  near  dunes. 

Wearing  and  rounding  of  telegraph-poles  in  deserts. 

Polishing  of  rocks  in  mountain  passes.  §§ 

Faceting  of  pebbles.  ||||     Examples. 

Effect  upon  vegetation. 

Toadstool-shaped  rocks  supposed  to  be  so  made  ;  often  due  to  softer  layers.  1T1F 
Origin  of  the  sand-blast  used  for  grinding  and  ornamenting  glass,  stone- 

carving. 
Wear  of  the  sand  grains  themselves.*** 

*  Woodbine  Parish's  Buenos  Ayres  and  the  Provinces  of  the  Rio  de  la  Plata.    127-128. 
t  The  earth  as  modified  by  human  action.    By  G.  P.  Marsh.    525-581    New  York,  1885. 
t  Dust  and  sand  storms  in  the  West.    By  J.  A.  Udden.     Pop.  Sci.  Mo.,  Sept.  1896,  p.  655. 
§  Across  America  and  Asia.    By  R.  Pumpelly.    59-60;  138-139.    London,  1870. 
Wind  as  a  factor  in  geology.    By  G.  P.  Merrill.    Eng.  Mag.,  Feb.  1892,  II,  596-607. 
|  Nature,  March  17,  1898,  LVII,  463. 

I  Darwinism.    By  Alfred  R.  Wallace.    362-374.    London  and  New  York,  1889. 
**  The  Russian  thistle  in  California.    Bui.  107,  Univ.  Cal.  Agr.  Exper.  Sta. 
Tumbling  mustard,  circular  no.  7,  U.  S.  Dept.  Agr.,  Div.  Bot. 

ft  Island  life.    By  Alfred  R.  Wallace.    London,  1880. 

it  Erosion  by  flying  sand  on  the  beach  of  Cape  Cod.    By  A.  A.  Julian.    Science.  Jan.  3, 
1902,  pp.  27-28. 

II  40th  parallel  rep.  II,  159.—  Blake,  Reconnaissance  in  California,  91-93.—  Am.  Jour.  Sci., 

Sept.  1855,  LXX,  178-181. 

Wind  action  in  Maine.    By  G.  H.  Stone.    Am.  Jour.  Sci.,  1886,  CXXXI,  133-138. 
II  J.  Walther.   Denudation  in  der  Wtiste.  Plates  IV,  V.    Leipzig,  1891.—  Max  Verworn 

Neues  Jahrb.  f.  Min.,  1896,  I,  200-210.-  Davis.    Proc.  Boston  Soc.  Nat.  Hist.,  XXVI, 

166-175;  plates. 
T,«j  Bui.  U.  S.  Geol.  and  Geog.  Surv.  Ter.,  IV,  1878,  p.  831;  1873,  pp.  32-6;  1874,  pi.  IV;  1875, 


p.  156.  —  Wheeler's  survey,  III,  82. 

ral  erosion  by  sand  in  Western  Territories.    By  G.  K. 

Sci.,  XXIII,  26-29.  —Die  Denudation   in  der  WUste.     Von  J.  Walther.      Leipzig, 


.       .  ,       ,      . 

Natural  erosion  by  sand  in  Western  Territories.    By  G.  K.  Gilbert.    Am.  Assn.  Adv. 


1891. 

On  the  laws  that  govern  the  rounding  of  particles  of  sand.    By  Wm.  Mackie.    Trans. 
Edin.  Geol.  Soc.,  1897,  VII,  298-311. 


16  ATMOSPIIKRIC    AGKNCIKS. 


III.  The  Depositing  of  Wind-Borne  Material.* 

Why  wind-borne  material  is  deposited. 

If  volcanic  dust  falls  in  water,  or  is  bedded,  it  makes  tuffs. 

If  rain  falls  through  dust,  it  falls  as  mud.t 

Wind-blown  sands  make  dunes. 


Fig.  3. — Sand-dunes  on  the  Sergipe  coast,  Brazil.    (Hartt.) 

Formation  and  shifting  of  sand-dunes. i 

Movement  of  dunes;  burial  of  houses;  invasion  of  towns  and   forests ;§ 

dune  helped  across  a  railway.  || 
Forms. 

1.  Lines  at  right  angles  to  wind  in  unobstructed  regions. 

2.  Lines  parallel  with  winds  in  regions  of  isolated  obstructions, 

such  as  bushes. 

Angle  of  repose  of  dry  Band,  35°;  wet  sand,  40°. 
Height. 

Probably  limited  only  by  accidents. 

On  the  coast  of  Holland,  260  feet. 

Western  Palestine,  200  feet.H 

On  Cat  Island,  one  of  the  Bahamas,  the  dunes  are  nearly  400 

feet  high ;  on  the  coast  of  West  Africa,  near  Cape  Bajador, 

they  are  500  feet  and  more.** 

*  The  mechanical  composition  of  wind  deposits.   By  J.  A.  Udden.    Augustana  Library. 

Publication  no.  1.     Rock  Island,  111.,  1898. 
t  Woodbine  Parish's  Buenos  Ayres,  137-128. 
J  On  the  formation  of  sand-dunes.    By  V.  Cornish.      Geog.   Jour.,   Mar.   1897,  pp.  278- 

309.    (Comprehensive  discussion.) 

Die  Denudation  in  der  Wiiste.    Von  J.  Walther.    Das  Wandern  der  Dunen,  513-22.     Leip- 
zig, 1891. 
Desert  sand-dunes  bordering  the  Nile  delta.     By  V.  Cornish.    Geog.  Jour.,  Jan.  1900, 

XV,  1-32.  -Nature,  Feb.  22,  1900,  LXI,  403. 
I  Report   on   a    botanical    survey   of    the  Dismal  Swamp  region.    By  T.  H.  Kearney. 

Contributions  U.  S.  Nat.  Mus..  vol.  V,  no.  6,  pp  332-337.     Washington,  1901. 
|  Climbing  and  exploration  in  the  Bolivian  Andes.   By  Sir  Martin  Conway.    55.    London, 

1901. 
f  The  survey  of  Western  Palest inc.    By  E.  Hull.    88.    London,  1886. —  On  the  maritime 

dunes  of  the  Low  Countries.     By  F.  C.  Winkler.  —  Report   of   the   International 


Congress  of  Geologists  for  1878,  pp.  181  et  seq. 
reconnaissance  of  the  Bahamas.    By 


**  A  reconnaissance  of  the  Bahamas.    By  Alex.  Agassiz.    Bui.  Mus.  Comp.  Zool.,  XXVI, 
no.  1,  p.  34.    Cambridge,  1894. 


18 


JEOLIAN    ROCKS. 


Structure. 

Due  to  methods  of  deposition. 

Variations  produced  by  shifting  winds. 
Length. 

Examples :  Monterey,  southwest  France,  Holland.* 

Damming  of  streams  on  west  coast  of  France  and  in  northeast 
Brazil,  t 


Fig.  4. — Sand-dune  structure  exposed  in  jeolian  sandstone. 

JEolian  rocks. 

JEolian  rocks  are  those  formed  of  wind-blown  materials,  usually  sands. 

They  are  not  necessarily  different  from  other  sandstones. 
Mostly  of  quartz  sand. 

In  Carson  Desert,  Nevada,  dunes  of  minute  crustacean  shells. 
Near  Fillmore,  Utah,  of  gypsum. 


Fig.  5.— ^Eolian  sandstones  forming  the  top  of  a  bluff  and  resting  upon  lava.    Fernando 
de  Noronha,  South  Atlantic. 


*For  physiographic  value  of  wind,  see  London  Geog.  Jour.,  1896,  VIII,  264-278. 
Subserial  deposits  of  the  arid  region  of  North  America.    By  I.  G.  Russell.    Geol.  Mag., 

1889,  pp.  289,  342-350. 
t  Les  Lacs  francais.    Par  A.  Delebeoque.    Paris,  1898. 


19 


20  CHANGES    OF   TEMPERATURE. 

Bermuda*  and  Bahamas  made  of  seolian  calcareous  sandstone. 
Process  by  which  such  rocks  are  hardened. 
Supposed  atolian  origin  of  the  loess  of  China;  2,500  feet  thick. t 

Cut  by  streams  into  gulches  30  to  100  feet  deep  and  4  to  20  feet  wide; 

houses  cut  in  these  walls. 
Influence  of  vegetation  on  seolian  deposits.* 

Probable  origin  of  the  "  hog-wallows  "  of  the  San  Joaquin  Valley,  Cali- 
fornia. § 
Similar  phenomena  to  be  seen  in  most  deserts. 


INDIRECT  WORK  OF  THE  ATMOSPHERE. 

The  indirect  work  of  the  atmosphere  is  more  important  than  its  direct 
work.  It  may  be  included  under  the  following  heads : 

1.  Changes  of  temperature. 

2.  Evaporation. 

3.  Production  of  waves  on  large  bodies  of  water. 

4.  Effect  on  the  water  level. 

5.  Effect  on  ocean  currents  and  climates. 

6.  Its  work  as  a  water  carrier. 

I.  Changes  of  Temperature. 

All  changes  of  temperature  cause  rocks  and  minerals  to  contract  and 
expand.  In  massive  or  crystalline  rocks  the  crystals  expand  and  contract 
differently  along  their  different  axes.  Some  even  contract  along  one  axis 
while  expanding  along  another.  || 

The  rocks  are  composed  of  several  minerals  interlocking ;  the  expan- 
sion and  contraction  at  different  rates  cause  the  minerals  to  slip  on  each 
other,  and  the  mass  to  loosen  and  disintegrate. 

*  Am.  Geol.,  May,  1897,  XIX,  293. 

The  geology  of  Bermuda.  By  Wm.  North  Rice.  Bui.  U.  S.  Nat.  Mus.,  no.  25,  p.  7.  Wash- 
ington, 1884. 

The  Bermuda  Islands.    By  A.  Heilprin.    32.    Philadelphia,  1889. 

The  seolian  sandstones  of  Fernando  de  Noronha.  By  J.  C.  Branner.  Am.  Jour.  Sci.,  April 
1890,  XXXIX,  247-257. 

The  Atlantic.    By  Sir  C.  Wy  ville  Thomson.    I,  285-295.    New  York,  1878. 

tChina.    By  F.  F.  von  Richthofen.    Reviewed  in  Am.  Jour.  Sci.,  1877,  CXIV,  487^91. 

F.  B.  Wright.  Science,  July  13,  1900,  XII,  71-72.-  G.  F.  Wright.  Bui.  Geol.  Soc.  Am., 
1902,  XIII,  127-128. 

Geological  researches  in  China,  Mongolia,  and  Japan.  By  R.  Pumpelly.  40-41.  Wash 
ington,  1866. 

The  distribution  of  loess  fossils.    By  B.  Shimek.    Jour.  Geol.,  VII,  122-140. 


Loess  as  a  land  deposit.    By  J.  A.  Udden.    Bui.  Geol.  Soc.  Am..  1897,  IX,  6-9. 
Eolian  origin  of  loess.     By  C.  R.  Keyes.    Am.  Jour.  Sci.,  CL.VI.  299-304. 
I  Across  Vatna  Jb'kul.    By  W.  L.  Watts.    76     London,  1876. 


Die  Denudation  in  der  Wilste  u.  ihre  Bedeutung.    Von  J.  Walther.    377.    Leipzig,  1891. 
§  Further  contributions  to  the  geology  of  the  Sierra  Nevadas.    By  H.  W.  Turner.    17th 

ann.  rep.  U.  S.  Geol.  Surv.,  1895-96,  pt.  I,  681-683.     Washington,  1896. 
The  hillocks  or  mound  formations  of  San  Diego,  California.    By  G.  W.  Barnes.    Am. 

Nat.,  Sept.  1879,  XIII,  S65-571. 

Hog  wallows,  or  prairie  mounds.      By  J.  Le  Conte.      Nature,  April  19,  1877,  XV,  530-531. 
|  Smithsonian  miscellaneous  collections,  XIV,  no.  289.    Tables  of  expansion  by  heat 

for  solids  and  liquids     By  F.  W.  Claru.    Washington,  1876. 


21 


EXFOLIATION. 


Changes  of  temperature  affect  surface  layers  especially. 

This  produces  spalling,  chipping,  and  exfoliation  in  layers. 
Tendency  to  produce  rounded  blocks ;  reason  for  the  rounding  of  cor- 
ners. 

Rounding  of  basaltic  columns;  examples. 
Called  "boulders  of  decomposition."* 
Same    effect    produced    on    hills  and 
mountains  of  massive  rocks  no- 
ticeable in  granite  region.     Ex- 
amples: Yosemite  Valley,  Serra 

do  Mar,  Rio  de  Janeiro,  interior  Fig.  6.-The  weathering  of  mas- 

....          _.          .                   ._  sive  rocks  along  joints  and 

Of   Africa,   Greorgia,t  and   North  the  formation  of  boulders 

Carolina.*  of  decomposition. 

Granite  and  gneiss  expand  one  part  in  about  200,000  for  every  ad- 
ditional degree  at  ordinary  temperatures. 

Annual  change  in  temperate  regions  is  about  150°  ( — 25°  to  +125° 
Fahr.)  for  exposed  surfaces. 

Linear  expansion  for  103°  over  a  surface  of  300  feet  =  1.85  inches. 


Fig.  7. — Granite  boulders  of  decomposition  in  the  Bay  of  Riode  Janeiro.    (Benest.) 


*  Winslow's  report  on  Iron  Mountain  sheet.    Missouri  Geol.  Surv.,  IX,  6-8,  plates. 

The  rocks  of  the  Sierra  Nevada.    By  H.  W.  Turner.    14th  ann.  rep.  U.  S.  Geol.  Surv., 

480,  and  plate  53.     Washington,  1895. 
t Merrill's  Rock-weathering.    Frontispiece. 
j  North  Carolina  and  its  resources.  Winston,  1896.  Plate  of  Stone  mountain.  Opp.  p.  115. 


23 


24  EXFOLIATION. 

Rifts  found  in  granite  quarries  caused  by  this  expansion  and  con- 
traction.*   (See  Plate  II.) 

When  the  temperature  falls  below  freezing  another  set  of  phenomena  is  intro- 
duced by  the  expansion  of  water  on  freezing. 
Lifting  of  sidewalks. 
Crumbling  of  damp  earth  by  needle-ice. 
Enlargement  of  crevices  in  rocks. 
Throwing  down  of  loose  fragments  and  blocks  from  cliffs. 

Case  of  Cleopatra's  Needle  in  New  York  City. 
Formation  of  talus  slopes. 
Disintegration  of  porous  rocks. 


Kig.  8.  -A  granita  peak  rounded  by  exfoliation,  Victoria,  Brazil.    (Hartt.) 

Importance  of  alternate  freezing  and  thawing. 

"Creep"  of  soil,  and  how  it  lowers  slopes;  examples  of  the  "knob- 
stone  "  hills  of  southern  Indiana. 

FORMATION  OF  SOIL  IN  PLACE. 

Relations  of  rocks  and  soils. 

Residuary  soils  formed  partly  through  changes  of  temperature  and  freez- 
ing, and  partly  through  the  chemical  action  of  water  and  plants. 
The  process  is  called  "  weathering."  t 

*See»  example  of  Raymond  quarry  in  12th  ann.  rep.  State  Min.  Bur.  California,  1894. 

384.    Sacramento,  1894. 
Decomposition  of  rocks   in  Brazil.    By  J.  C.  Branner.    Bui.  Geol.  Soc.  Am.,  1896,  VII, 

255-314. 

Principles  of  rock  weathering.  By  G.  P.  Merrill.  Jour.  Geol.,  1896,  IV,  704-724;  IV,  850. 
Boulders  formed  in  situ.  By  G.  H.  Barton.  Technology  Quarterly,  V,  401-405.  Boston,  1892. 
Plate  XIV  in  monograph  XXVII,  U.  S.  Geol.  Surv. 

A  treatise  on  rocks,  rock- weathering,  and  soils.    By  G.  P.  Merrill.    New  York,  1897. 
t  Concentric  weathering  in  sedimentary  rocks.    By  T.  C.  Hopkins.    Bui.  Geol.  Soc.  Am., 

IX,  427-428. 
Weathering  of  diabase  in  the  vicinity  of  Chatham,  Va.    By  T.  L.  Watson.    Am.  Geol., 

Dec.  1899,  XXIV,  355. 


Plate  III.  —  A  cave  room,  made  by  the  exfoliation  of  granite,  in  San 
Jacinto  Mountains,  Riverside  County,  California.     (McMillan.) 


25 


26  EVAPORATION. 

Why  some  blocks  of  rock  are  left  undecayed.* 
Why  soil  is  often  thin  on  slopes  and  deeper  in  the  valleys. 
Alluvial  soils  derived  from  residuary  soils. 
Method  of  accumulation. 
Origin  of  soil  belts. 

Glacial  soils  are  derived  largely  from  residuary  soils. 
Accumulation  and  modification. t 


Fig.  9.— Talus  slopes  on  the  side  of  Mount  Sneffels,  Colorado. 

II.  Evaporation. 

The  geological  work  of  evaporation  consists  in  the  concentration  and 
deposition  of  minerals  dissolved  in  water,  the  drying  up  of  streams  in  arid 
regions,  and  in  the  drying  out  of  certain  soils,  which  causes  them  to  open 
in  cracks  that  admit  water  and  gases  to  the  soils  and  the  underlying  rocks. 
The  chemical  deposition  of  minerals  will  be  treated  at  length  under  the 
head  of  Chemical  Agencies. 

Formation  of  efflorescence. t 

Illustrated  by  efflorescence  on  brick  buildings. 

Effect  of  the  formation  of  efflorescence  upon  certain  rocks.    The  origin 

of  "fret- work."  § 
"Alkali  "  of  arid  regions. 

*  U.  S.  Geol.  Surv.,  monograph  XXVII,  plate  XIV,  286.    Washington,  1896. 

fThe  origin  and  nature  of  soils.    By  N    S.  Shaler.    12th  ann.  rep.  U.  S.  Geol.  Surv., 

213-545.    Washington.  1892. 

Geology  of  England  and  Wales.    By  H.  B.  Woodward.    518-550.    2d  ed.,  London,  1887. 
t  Journal  of  the  Franklin  Institute,  CVI,  52. 

American  Architect,  1884,  XVI,  207-208,  267-268;  1893,  XXXIX,  30. 
The  Clay  Worker,  April  1893,  pp.  497-509;  Dec.  1896,  pp.  443-444;  Feb.  1897,  pp.  124-125;  June 

1897,  p.  517;  Oct.  1897,  p.  265. 

The  Clay  Record,  Nov.  15,  1897,  XI,  17:  July  8,  1898,  XIII,  15. 
g  See  example  in  monograph  XXXIII,  U.  S.  Geol.  Sury.,  362. 


ORIGINAL  CONDITION  OF  THET    ROCKS. 


*~k^"T"°'°fcL   "•f~-r.-°  rt'"r'""\~g''T .*;";";•_.••  '."••" '.''- "\  :    i^g£& 


-  h-  _  *-,.  t—i  ^—  ^  i— _  ^-1  fa— 
r>—  &=_ —  r=^-—  f=-— -  £=--=-—  i^iirE^— _ 
zp^T^-T  -^=ri=-_^T=--  feJl  &= 


FIRST  STAGE  OF  DECOMPOSITION. 


SECOND  STAGE:  OF  DECOMPOSITION, 


THIRD   STAQE  OF  DECOMPOSITION. 


IBOONE  CHERT  MANGANESE-BEARING  CLAY  EEaizARD  LIMESTONE 

I  ST.CLAIR  LIMESTONE;  IZi3sACCHARoiDAL  SANDSTONE 


Plate  IV. —  Theoretical  sections  showing  the  process  of  irregular  rock  decomposition 
and  the  formation  of  soil.     (Penrose.) 


27 


28 


EVAPORATION. 


All  spring,  well,  or  surface  waters  contain  mineral  matter  in  solution. 
How  demonstrated. 

Water  passing  through  rocks  and  soils  dissolves  some  of  the  soluhle  minerals. 

In  arid  regions  surface  evaporation  causes  water  to  come  to  the  surface 
from  below  or  within,  and  its  evaporation  leaves  the  mineral  in 
small  crystals  over  the  surface.  Called  "alkali";  various  sub- 
stances, such  as  sulphate  of  magnesia,  sodium  chloride,  etc.* 


Fig.  10. — Fret-work  in  the  yellow  sandstone  of  the  Santa  Cruz  Mountains. 

*  Alkali  lands.     By  Milton  Whitney  and  T.  H.  Means.     Farm.  Bui.  88,  U.  S.  Dept.  Agr. 

Washington,  1899. 
The  alkali  soils  of  the  Yellowstone  Valley.    By  M.  Whitney  and  T.  H.  Means.    Bui.  14, 

Div.  Soils,  U.  S.  Dept.  Agr.    Washington,  1898. 


30 


WINDS   AND    WAVES. 


Efflorescence  often  causes  rock  surfaces  to  disintegrate  and  cavities  to 

form. 

Efflorescence,  being  soluble,  is  washed  off  by  rain. 
Origin  of  the  "whitewash"  of  brick  buildings. 


III.  Production  of  Waves  on  Large  Bodies  of  Water. 

Waves  are  one  of  the  most  im- 
portant geologic  agents. 

Most  waves  are  produced  by  wind 
moving  over  water. 

The  geologic  work  of  waves  is 
done  at  the  shore  line. 

If    water    were    undisturbed    it 

would  not  cut  land. 
(The  geologic  work  of  waves 
is  treated  at  length  un- 
der the  head  of  Aque- 
ous Agencies.) 

Abruptness  of  sea  and  lake  shores 
due  chiefly  to  the  under- 
cutting of  waves. 

Skeleton  islands  off  coasts  and 
attacked  shores. 

Transportation  of  shingle  and 
sand  along  shores. 

Formation  of  spits.  (Discussed 
under  Aqueous  Agencies.) 

Damming  of  river  mouths  by  wave-driven  sands. 
California. 


Fig.  11.— Streams  near  Oceanside  dammed  by 
beach  sands  heaped  across  their  mouths. 


Example:  Oceanside, 


IV.  Effect  of  Wind  on  Water  Level. 

Blowing  of  wind  for  a  long  time  in  one  direction  over  a  body  of  water 

tends  to  pile  up  the  water. 
Examples  in  long,  narrow  lakes,  such  as  the  "finger  lakes"  of  New 

York;  on  Bala  Lake;  Mediterranean  Sea;*  Red  Sea. 
In  October,  1886,  the  west  wind  on  Lake  Erie  raised  the  water  8  feet 

at  Buffalo  and  lowered  it  8  feet  at  Toledo,  Ohio.t 

September  8,  1900,  the  city  of  Galveston,  Texas,  destroyed  by  a  flood 
blown  by  southeast  winds  8  or  9  feet  above  usual  high- water 
level. t  Similar  earlier  disasters. § 


*  Karamania.    By  F.  Beaufort.    20,  21,  116.    2d  ed.,  London,  1818. 

t  Nat.  Geog.  Mag.,  Sept.  1897,  VIII,  238. 

I  The  lessons  of  Galveston.    By  W.  J  McGee.— The  West  Indian  hurricane  of  Sept, 

1-12,  1900.    By  E.  B.  Garriott.    Nat.  Geog.  Mag.,  Oct.  1900,  XI,  377-392. 
§  Gen.  A.  W.  Greeley,  in  Nat.  Geog.  Mag.,  Nov.  1900,  XI,  442-445. 


31 


32  WINDS    AND    CURRENTS. 

Tides  are  unusually  high  when  the  wind  helps. 

Effect  of  southeast  winds  on  the  tides  in  the  Bay  of  Fundy.* 
Higher  tides  increase  the  range  of  wave-cutting. 

V.  Effects  of  Winds  on  Ocean  Currents  and  Climate. t 

Character  and  direction  of  ocean  currents. 

Ocean  currents  are  produced  partly  by  the  lagging  of  water  on  the  re- 
volving globe. 

The  atmosphere  as  a  whole  lags  in  much  the  same  way,  but,  being 
heated  at  the  equator,  it  rises  and  flows  toward  the  cold  poles. 
This  produces  currents  in  contact  with  the  globe,  chiefly  a  water  sur- 
face, which,  as  they  move  toward  the  equator,  lag,  and  hence  swing 
westward. 

These  air  currents  help  on  the  ocean  currents  which  tend  to  pile  up  the 
water.    In  the  Gulf  of  Mexico  it  escapes  as  the  "Gulf  Stream" 
into  the  North  Atlantic. 
Probably  only  the  surface  currents  are  determined  by  winds,  while  the 

deep  currents  are  due  largely  to  convection.! 

In  1882  severe  northwest  gales  pushed  aside  the  warm  gulf  waters 
off  the  New  England  coast,  and  the  coldness  of  the  waters 
killed  the  tile-fish  by  the  millions.^ 

Climatic  effect  of  the  warm  waters  carried  into  polar  regions. 
Example  of  northwestern  Europe  and  Iceland. 

VI.  The  Atmosphere  as  a  Water  Carrier. 

The  air  is  never  still. 

The  great  air  currents  are  more  or  less  definite,  but  they  are  influenced 
by  the   seasons    (owing    to    changes  of  temperature),  and,  to 
some  extent,  by  topographic  forms.  || 
Warm  air  takes  up  moisture. 

When  this  air  is  cooled  the  moisture  is  condensed  and  dropped. 
Cloud  banners  on  mountain  peaks. 

Moisture  on  the  inside  of  window-panes  in  cold  weather. 
Causes  of  the  sweating  of  roi-ks. 
Warm  air  rises. 

In  the  tropics,  over  warm  seas,  it  absorbs  the  moisture  and  carries  it 

upward.     This  afterward  comes  down  as  rain. 
Abundant  rains  of  the  Andes  due  to  east  winds. 
Why  it  is  dry  on  the  west  slope  of  the  Andes. 

*  G.  P.  Matthew.    Canadian  Naturalist,  new  ser.,  IX,  369,  foot-note. 

t  The  influence  of  the  winds  upon  climate  during  the  Pleistocene  epoch.    By  F.  W.  Har- 

mer.    Quar.  Jour.  Geol.  Soc.,  LVII,  405-478.    London,  1901. 
t  W.  M.  Davis.    Scot.  Geog.  Mag..  Oct.  1897. 
g  C.  C.  Nutting.  Science,  May  31,  1901,  XQI,  843. 
B  The  circulation  of  the  atmosphere.    By  W.  M.  Davis.     Quar.  Jour.  Roy.  Meteor.  Soc., 

April  1899,  XXV,  no.  llu. 


34  WIND    A   WATER   CARRIER. 

When  the  temperature  into  which  the  water-laden  air  is  brought  is  below 
freezing  the  precipitation  is  frozen  —  that  is,  it  is  in  the  form  of  frost, 
hail,*  or  snow. 
Frost  on  window-panes,  instead  of  water,  when  it  is  freezing  cold  on 

the  pane. 
Why  there  is  snow  only  about  the  poles  and  on  the  highest  mountains. 

Why  there  is  usually  no  snow  in  the  coldest  weather. 
Sleet  and  hail  start  high  and  freeze  before  reaching  the  earth. 
Importance  of  water  to  life. 

Water  is  one  of  the  first  conditions  of  existence :  no  life  without  it. 
The  most  important  geologic  work  done  by  the  atmosphere  is  that  which  it 

does  as  a  water  carrier. 

All  the  geolgic  work  done  by  water  is  indirectly  the  work  of  the  atmosphere . 
Of  the  atmosphere  in  general. 

The  exposure  of  rocks  to  the  air  is  fatal  to  the  rocks. 
They  are  almost  universally  broken  up  and  destroyed. 
They  can  last  only  when  protected  from  the  atmosphere. 
Rock  destruction  is  chiefly  a  subaerial  process. 


Fig.  12.— Stone-capped  columns  of  earth  and  rock  fragments  near  Canyon  City,  Colorado. 
(Purdue.) 

*  Method  of  formation  of  hail.    Nature,  Jan.  31,  1901,  LXIII,  337. 


35 


AQUEOUS    AGENCIES. 


MECHANICAL  AQUEOUS  AGENCIES. 

The  mechanical  work  of  water  is  done  by  — 

1.  Rain  (in  its  direct  work). 

2.  Streams. 


4.  Seas  and  oceans. 

5.  Ice  in  forming  and  as  glaciers  and  icebergs. 

I.  The  Mechanical  Work  of  Rain. 

Most  of  the  mechanical  work  of  rain  is  done  after  the  water  gathers  in 


The  impact  of  rain,  however,  .produces  certain  peculiar  topographic  forms, 
illustrated  by  the  stone-capped  columns,  or  earth  pillars,  of  Tyrol,* 
and  of  La  Paz  Valley,  Bolivia.! 

Aside  from  that  which  evaporates,  the  water  of  rain  runs  off  as  streams 
(p.  38),  or  soaks  into  the  ground  and  emerges  as  springs,  either  on 
land  or  beneath  the  ocean. 
Landslides,  or  landslips. 

Landslides  are  mechanical  effects  produced  by  rain-water  soaking  the 

ground. 
Common  in  railway  cuts,  and  wherever  the  natural  support  of  the  soil 

has  been  removed. 

Overwhelming  villages  in  Switzerland,}  Russia,?  Colorado, ||  Washing- 
ton.^    The  bursting  of  peat- bogs**  in  Ireland. 

Mud  avalanches  in  India.tt  the  Alps,}*  and  the  Andes.§$ 
Landslips  sometimes  dam  streams  and  thus  form  lakes. |||| 

*  Geikie's  Text-book  of  geology,  354-356. 

t  The  Bolivian  Andes.    By  Sir  Martin  Conway,  93.    London,  1901. 

t  Science,  Jan.  1,  1897,  p.  21. 

Bui.  Soc.  Geol.  de  France,  2me  ser.,  VII.  188.    Paris,  1850. 

Ueber  Bergstttrze  in  den  Alpen.     Von  Dr.  A.  Baltzer  in  Zurich.     Sep.  Abdr.  Jahrbuch 

des  S.  A.  C.,  X,  Zurich,  1875. 

g  Guide  des  excursions  du  VII  Cong.    Gtk>l.  Internat.  XX,  30,  and  plate  C.    St.  Peters- 
burg, 1897. 

II  W.  Cross.  Science,  Dec.  25,  1896,  IV,  962. 
11 1.  C.  Russell.    Bui.  108,  U.  S.  Geol.  Surv.,  47-48. 
20th  ann.  rep.  U.  S.  Geol.  Surv.,  part  II,  193-200. 
**  G.  A.  J.  Cole.    Nature,  Jan.  14,  1897,  IV,  254-256. 
G.  Henry  Kinahan.    Nature,  Jan.  21,  1897,  LV,  268-269. 
Jour.  Geol.,  1901,  IX,  639. 

tt  Climbing  and  exploration  in  the  Karakorum  Himalayas.    By  W.  M.  Conway.    118, 129. 
130.    New  York,  1894. 

t  Bonney.    Geol.  Mag.,  Jan.  1902.  p.  8. 

:  The  highest  Andes.    By  E.  A.  Fitzgerald.    23-24.    New  York,  1899. 
G.  K.  Gilbert.    Science,  Jan.  19,  1900.  XI,  p.  99. 

'    i  Nation,  Mar.  4,  1897. 


37 


38  WORK    OF    STREAMS. 

Conditions  favoring  landslides : 

1.  Topographic  form;  only  in  mountains  and  hills. 

2.  Geologic  structure. 

3.  Mineralogic  composition. 

Clays,  kaolin,  decayed  shale,  serpentine,  steatite,  soapstone, 
graphite,  mica,  and  peat  are  all  slippery  when  wet. 

4.  Water  present.* 

5.  Earthquakes.! 
How  to  prevent  landslides. 

1.  By  draining  and  turning  the  water  away  from  the  slippery  earth. 

2.  By  planting  trees  where  roots  will  hold  the  soil. 

3.  By  protecting  the  natural  supports  of  land  liable  to  slip. 

Case  of  the  reservoir  at  Rio  de  Janeiro. 

II.  The  Mechanical  Work  of  Streams. 

Origin  of  streams. 

Relation  to  underground  water  supply. 

Relation  to  surface  waters. 
The  mechanical  work  of  streams. 

1.  Erosion,  or  wearing. 

2.  Transportation,  or  carrying. 

3.  Deposition. 

The  whole  process  of  removal  is  generally  spoken  of  as  denudation. 
The  laws  of  flow  in  open  streams. 

Different  rates  of  surface,  bottom,  and  sides  of  streams. 
Different  rates  at  bends. 

Difference  due  to  internal  friction  as  well  as  to  friction  against 
the  channel. i 

I.  STREAM  EROSION. 
Stream  erosion  is  produced  in  two  ways : 

1.  By  impact  of  the  water. 

2.  Scour,  or  abrasion,  by  the  transported  materials. 

I.  Erosion  by  impact  against  soft  materials  affects  the  bottoms  and  sides  of 

stream  channels. 
Illustrated  by  hydraulic  mining. 

*  On  landslides  in  Switzerland,  see  Neues  Jahrb.  fur  Min.  u.  Geol.,  1877,  p.  916;  1875,  p.  15. 
Modern  denudation  in  North  Wales.  By  J.  R  Dakyns.  Geol.  Mag.,  Jan.  1900,  pp.  18-20. 
Notes  on  the  late  landslip  in  the  Dendenong  Ranges,  Victoria.  By  F.  D.  Power.  Proe. 

Austral.  Assn.  Adv.  Sci.,  1893,  IV,  337-340. 
Articles  on  landslides  cited  in  British  Assn.  Rep.,  1885,  pp.  448,  451,  458.— Edin.  New  Phil. 

Jour.,  1840,  XXIX,  160. 
Topographic  features  due  to  landslides.    By  I.  C.  Russell.    Pop.  Sci.  Mo.,  Aug.  1898, 

LIII,  480-489. 
Geology  of  the  Cascade  Mountains  in  Northern  Washington.     By  I.  C.  Russell.     20th 

ann.  rep.  U.  S.  Geol.  Surv.,  part  II.  Landslides,  193-204. 
Thecauseof  the  Darjeeling  landslips.    Nature.  Dec.  7,  1899,  LXI,  127.— Dawson,  in  Bui. 

Geol.  Soc.  Amer.,  1899.  X,  484-490. 
t  The  great  Indian  earthquake  of  June  12,  1897.    By  J.  Milne.    Nature,  Oct.  13,  1898,  p. 

586. 
I  See  results  of  Seddon,  Trans  St.  Louis  Acad.  Sci.,  1898,  VJII,  p.  xxiv. 


40  WORK    OF    STREAMS. 

Lateral  erosion  undercuts  banks  of  soft  materials. 

Centrifugal  force  on  the  outside  of  a  stream's  curves. 

Lateral  erosion  operates  chiefly  in  the  lower  part  of  a  river's  course. 

Produces  winding  streams. 

Swinging  of  streams  from  side  to  side. 

Ox-bows  and  "  cut-offs  "  of  the  Mississippi  River. 

Mompox,  an  old  Spanish  city,  fifty  years  ago  stood  on  the 
bank  of  the  Rio  Magdalena.     Owing  to  the  shifting  of 
the  stream  it  is  now  twenty  miles  from  that  river.* 
An  old  adobe  town  that  formerly  stood  on  the  banks  of  the 
Colorado  river  below  Needles  is  now  (1902)  five  miles 
inland.    The  falling  of  the  undercut  river  banks  may  be 
heard  all  night.     (V.  L.  Kellogg.) 
Terras  cahidas  of  the  Amazonas.t 

Formation  of  river  terraces.     (See  under  Physiography.) 
II.  Erosion  by  scour,  or  abrasion  (of  bottom  and  sides),  by  transported  ma- 
terials.* 
Materials  moved : 

Blocks      )    „ 

~  ,  ,  ,        }-  Boulders. 

Cobbles    ) 

Pebbles. 
Sand. 
Clay. 
Effects  of  moving  stones  and  sand. 

Clear,  clean  water  cannot  cut  hard  rocks  mechanically. 
1.  To  grind  rock  beds  and  sides  of  streams.     (Abrasion.) 
In  eddies  below  cataracts  and  falls,  form  pot-holes, 
Methods  of  grinding. 
Searsville  Creek. 

Archbald  pot-hole,  40  by  20  feet.$ 
Lucerne,  Switzerland. 
Pot-holes  are  purely  local. 

General  effect  of  the  grinding  of  the  bottom  is  to  cut  stream  channels 
deeper  in  the  rocks.  The  loose  stones,  sand,  etc.,  are  pushed 
along  down  stream,  and  as  they  go  they  wear  and  cut  the  bottom 
and  sides.  Bottom  cutting  is  done  chiefly  in  the  upper  and 
steeper  parts  of  stream  channels. 

*  Colombian  and  Venezuelan  Republics.    By  W.  L.  Scruggs.    44.    Boston,  1900. 

t  The  pororoca  or  bore  of  the  Amazon.    Science,  Nov.  28,  1884. 

t  The  erosive  power  of  rivers  and  glaciers.    By  R.  M.  Deely.    Geol.  Mag.,  Sept.  1897,  p. 

§  Glaciation  of  the  Wyoming  and  Lackawanna  valleys.     By  J.  C.  Branner.     Proc.  Am. 

Phil.  Soc.,  1886,  pp.  353-356. 
Archbald  pot-hole.    By  C.  A.  Ashburner.    2d  Geol.  Surv.  of  Pa.,  ann.  rep.  for  1885,  pp. 

615-635,  and  plates. 
Glacial  pot-holes  in  California.    By  H.   W.   Turner.     Am.  Jour.  Sci.   Soc.,  Dec.  1892. 

XLJV,  453-489,  and  plate. 

Open-air  studies.    By  G.  A.  J.  Cole.    30-32.    London,  1895. 
A  glacial  pot  hole  in  the  Hudson  river  shales  near  Catskill,  N.  Y.     By  H.   F.  Osborn. 

Am.  Nat.,  Jan.  1900,  XXXIV,  33-36. 


41 


42  WORK    OF   STREAMS. 

2.  To  bump  together  the  materials  moved .     (Corrasion.) 
Process  one  of  wearing,  chipping,  and  rounding.* 
Illustrated  by  the  manufacture  of  playing  marbles.t 
Pebbles  and  boulders  are  rounded  in  the  same  way. 


Fig.  13.—  The  glacial  pot-hole  at  Archbald,  Pa.     From  a  photograph  taken  with  the 
camera  pointing  straight  upward. 


*  Description  of  apparatus  and  methods  used  by  the  Mass.  Highway  Commission    et 

By  T.  C.  Mendenhall,  etc.    Stone,  April  1899,  XVIII,  207-210 

*  The  non-metallic  minerals.   By  G.  P.  Merrill.    Rep.  U.  S.  N»t.  Mus.,  1899,  p.  370. 


43 


44  WORK   OF   STREAMS. 

Rounded  worn  pebbles  are  made  only  by  the  action  -of  water  as 

streams  or  waves. 

Why  some  pebbles  are  round,  some  flat,  and  some  long  and  slender. 
How  water-worn  stones  throw  light  on  the  history  of  rock  beds. 
Rounding  of  sand  grains  can  be  produced  only  when  the  current  is  not 
strong  enough  to  suspend  the  grains,  but  yet  strong  enough  to 
move  them.    This  allows  them  to  bump  over  each  other  like 
pebbles.     Very  fine  sand  is  angular. 
Size  of  sand  grains  in  relation  to  form. 
Specific  gravity. 

Hardness  prevents  rapid  wearing. 
Distance  traveled. 

Agent  of  transportation,*  wind,  water,  ice. 

The  power  of  a  stream  to  wear  its  channel  is  increased  or  kept  up  by 
the  removal  by  the  current  of  the  material  thus  produced. 

II.  STREAM  TRANSPORTATION. 

Muddy  color  of  some  streams,  and  milky  color  of  glacial  streams,  due 
to  matter  carried. 

Law  of  the  transporting  power  of  water: — 

Erosive  power,  or  power  to  overcome  cohesion,  varies  as  the  velocity 

squared. 

That  is,  velocity  doubled  quadruples  the  force  of  the  current. 
Transporting  power,  or  power  to  overcome  weight,  varies  as  the  sixth 

power  of  the  velocity. 
That  is,  double  the  current  and  it  will  move  sixty-four  timer 

as  big  a  block. 
Or,  increase  the  velocity  ten  times  and  it  will  transport  a  block 

one  million  times  as  large.t 

Vast  importance  and  enormous  increase  of  work  done  by  increase  of 
velocity  of  streams. 

Currents  required  to  move  materials  in  rivers : 

Clay  requires 0.25  feet  per  second 

Fine  sand 50        "     " 

Pebbles  size  of  pea 1.00        "     " 

Pebbles  1  inch  in  diameter 2.25        "     " 

Blocks  of  5  tons 15.  "     " 

Blocks  of  320  tons 30.  "      " 

Result  of  dumping  all  these  in  a  stream  at  once. 

*  On  the  laws  that  govern  the  rounding  of  particles  of  sand.     By  Wm.  Mackie.    Trans. 

Edin.  Geol.  Soc..  1897,  VII,  298-311. 

t  Prestwich's  Geology.    I,  83.—  Quar.  Jour.  Geol.  Soc.,  IV,  92-93. 
Geologic  pratique.    Par  Elie  de  Beaumont.    Du  regime  des  rivieres.    Tome  II,  63-134. 

Paris,  1849. 

Ann.  rep.  U.  S.  Engineers,  1875,  II,  481. 

A  treatise  on  hydraulics.    By  M.  Merriman.    251-252.     New  York.  1891. 
The  suspension  of  solids  in  flowing  water.    By  E.  H.   Hooker.     Trans.  Am.  Soc.  Civ. 

Eng.,  1896,  XXXVI,  239-340. 
(The  last  work  contains  a  valuable  bibliography  of  the  subject.) 


45 


46  WORK    OF   STREAMS. 

The  total  result  of  these  varying  carrying  capacities  is  the  sorting  action 
of  water,  and  the  deposition  at  separate  places  of  coarse  and  fine  materials. 
Importance  of  the  varying  currents  caused  by  fluctuation  in  the  volume  of 
water  during  freshets. 

In  regions  of  concentrated  rainfall  the  stream  work  is  likewise  concen- 
trated— very  large  part  of  the  time,  and  nil  the  rest  of  the  year. 
The  materials  carried  mechanically  by  streams  are  mostly  submerged. 
Some  streams  upon  swelling,  especially  in  arid  regions,  carry 
sand  and  small  stones  upon  the  surface  of  the  water,  held  up  by 
tension.* 
Determination  of  the  amount  of  transportation  by  streams. 

I.  By  reconstruction  or  restoration  of  the  topography,  or  of  matter  removed. 

In  canons  of  horizontal  rocks.  In  folded  regions  by  restoring  the 
arches  and  folds.  Of  limited  application  owing  to  ignorance  of 
the  upper  limit  of  the  surface  removed. 

Only  part  of  the  record  preserved. 

II.  By  measuring  the  discharge  of  drainage,  and  estimating  the  amount  of 

sediments  carried  out. 

Origin  of  the  silts  of  any  stream. 

Relations  to  its  hydrographic  basin. 

Observations  on  the  amount  carried  in  each  gallon,  and  the  number  of 
gallons  discharged. 

Method  of  measuring  discharged 

Collecting  samples  at  various  depths,  and  in  various  parts  of  the  stream. 

Objects  of  the  method. 

Illustrated  by  work  on  the  Arkansas  river. 

How  to  determine  the  amount  of  silt  in  discharge. 

The  Arkansas  river  in  1887-88  carried  2  grains  of  silt  per  gallon  at  the 
lowest  stage,  and  713  grains  per  gallon  at  the  highest  stage. 

In  November,  1887  (lowest  discharge  in  any  month),  the  total  dis- 
charge of  silt  was  16,449  tons  (dry). 

In  May,  1888,  it  was  6,208,717  tons.  Total  for  the  year  was  21 ,471 ,578 
tons.t 

III.  By  direct  measurement  of  wear  on  stream  beds.§ 
Rates  of  erosion  and  transportation  by  streams. 

Erosion  of  the  hydrographic  basin  of  the  Arkansas  above  Little  Rock 
(=  140,000  square  miles)  takes  place  at  the  rate  of  one  foot  in 
9,433  years. 

Over  the  Mississippi  basin  (1,317,500  square  miles)  the  rate  is  one  foot 
in  4,640  years. 

*  Floating  sand.    By  F.  W.  Simonds.    Am.  Geol.,  Jan.  1896,  XVII,  29-37. 

"Floating  stones."    Nature,  Feb.  1,  1900,  LXI,  318;  Feb.  8,  1900,  LXI,  346. 

Science,  Mar.  30,  1900,  XI,  510-512;  June  8,  1900,  XI,  912-913. 

t  Instruments  and  methods  of  hydrographic  measurements.     By  F.  H.  Newell.     Proc. 

Am.  Assn.  Adv.  Sci.,  XLVII.  248-249. 
I  Erosion  in  the  hydrographic  basin  of  the  Arkansas  river  above  Little  Rock.     By  J.  C. 

Branner.    Ann.  rep.  Geol.  Surv.  of  Ark.  for  1891,  II,  153-166.    Little  Rock,  1894. 
t>  The  rate  of  erosion  of  some  river  valleys.    By  C.  C.  Brittlebank.  Geol.  Mag.,  July  1900, 

y-JT       «w*rt      rtArt 


47 


48  WORK    OF    STREAMS. 

Amazon  basin  2,264,000  square  miles.     Drainage  is  not  always  propor- 
tional to  the  area.     Amazon  hydrographic  basin  has  twice  the 
area  of  Mississippi  and  five  times  the  water,  owing  to  greater 
rainfall  under  the  tropics. 
The  rate  of  mechanical  erosion  by  streams  depends  on  — 

1.  The  volume  of  water.     Small  stream  cannot  carry  much. 

2.  The  slope  of  the  land,  which  determines  the  velocity  of  the  streams. 

3.  Character  of  the  rocks.     The  softer  rocks  are  cut  faster. 

4.  Quality  and  quantity  of  detritus,  or  load.    The  hard  rocks  cut 

faster;  too  much  chokes  up  or  overloads  the  stream. 

5.  Climatic  conditions.   Differences  between  dry  and  wet  climates,  and 

especially  difference  between  a  region  of  concentrated  rainfall 
and  one  having  the  same  rainfall  distributed  throughout  the 
year.    Differences  between  tropics  and  cold  climates.     Freezing 
loosens  soil  and  rock. 
The  results  of  erosion  and  transportation  are  local  and  general. 

I.  LOCAL  RESULTS. 

The  local  result  of  erosion  and  transportation  is  to  produce  gullies,  chan- 
nels, gorges,  waterfalls,  and  valleys.  The  smallest  ones  we  see  made ; 
larger  ones  take  more  time,  but  the  process  is  the  same.    The  Colo- 
rado canon,  a  most  striking  illustration,  is  2,000  to  6,000  feet  deep. 
The  Colorado  river  rises  in  the  Uintah  and  Rocky  Mountains  in  rainy 
areas,  but  it  flows  through  an  arid  region  where  there  is  but 
little  frost  to  break  up,  and  but  little  rain  to  wash  down  the 
banks. 
Origin  of  waterfalls. 

Waterfalls  are  necessarily  in  stream  channels. 

I.  Caused  by  a  more  resisting  bed  overlying  less  resisting  ones. 

Niagara  as  a  type. 

Why  most  waterfalls  are  in  gorges. 

Time  is  required  to  cut  back. 

II.  Caused  by  a  new  escarpment    formed  across   stream    channel. 

These  escarpments  may  occur  — 

1.  On  coasts  where  encroachment  is  more  rapid  than  the  cutting  of 

the  streams. 

2.  In  rapidly  cut  canons,  with  falls  in  the  side  streams. 

3.  On  the  up-stream  sides  of  faults  across  streams. 
All  valleys  are  more  or  less  the  results  of  stream  erosion. 

Some  valleys,  though  modified  by  stream  erosion,  are  formed  as  — 

1.  Fault  valleys. 

2.  Synclines. 

3.  Between  volcanic  mountains. 

4.  Glacial  valleys.     These  are  small.* 

*  Technology  Quarterly,  X,  fig.  27,  opp.  p.  242. 


50  STREAM    DEPOSITION. 


II.  GENERAL  RESULTS. 
The  general  result  of  erosion  and  transportation  (or  of  denudation),  as 

distinguished  from  the  local  result,  is  a  lowering  of  land  surfaces. 
Demonstrated  in  cases  of  large  streams. 
Origin  of  the  silts  carried  by  streams. 
They  come  from  the  whole  basin,  though  some  parts  are  attacked 

more  rapidly  than  others. 

Every  part  of  the  land  above  water  is  attacked  by  agencies  of  decom- 
position and  denudation. 

The  present  contour  of  the  land  reveals  little  or  nothing  of  its  original 
form. 

The  base  level  of  erosion  or  peneplain.* 

III.  DEPOSITION. t 

Deposition  by  a  stream  takes  place  in  accordance  with  the  laws  of  trans- 
portation. 

If  the  stream  were  uniform  in  velocity  throughout  there  would  be  no 
deposition ;  but, 

When  any  part  of  a  loaded  current  is  checked,  deposition  takes  place. 

In  winding  streams  silts  deposit  on  the  inside :s  of  curves. 

Why  ox-bows  are  silted  up  next  to  the  main  stream  and  then  cut  off 
and  left  as  crescent-shaped  lakes. 

Eddies  silt  up  when  the  current  is  slack,  but  keep  clear  when  the  cur- 
rent is  strong,  so  that  there  is  alternate  removal  and  deposition  at  any 
single  place. 

SOME  IMPORTANT  INSTANCES  OF  STREAM  DEPOSITION. 

1.  Deposition  over  flood-plains. \ 

Flood-plain,  that  part  of  a  valley  that  is  covered  by  water  when  the 

stream  is  in  flood. 
General  silting  up  of  bottom-lands. 

2.  Formation  of  natural  levees. 

Levee  bank  is  raised  next  to  the  stream. 

How  the  current  on  an  overflowed  flood-plain  clings  to  its  channel. 

A  little  of  the  main  current  constantly  leaving  the  channel  is  checked 

by  the  quiet  waters;  this  causes  silts  to  sink  along  the  margin 

of  the  main  stream. § 
When  the  main  stream  overflows,  the  side  stream  deposits  part  of  its 

load  as  soon  as  it  is  checked. 

*  The  peneplain.    By  W.  M.  Davis.     Am.  Geol.,  April  1899,  XXIII,  207-239. 

t  Denudation  and  deposition.     By   G.  J.  Stoney.      Phil.  Mag.,  XLVII,  372-375;  557-565. 

London,  1899. 

Denudation  and  deposition.    By  Ch.  Chree.     Phil.  Mag.,  XLVII,  494-496.     London,  1899. 
I  Recognition  of  river  and  flood  deposits.    By  W(arren)  U(pham).     Am.    Geol.,  May 

1900,  XXV,  313-314. 
§  The  suspension  of  solids  in  flowing  water.    By  E.  H.  Hooker.    Trans.  Am.  Soc.  Civ. 

Eng.,  XXXVI,  239-340.     New  York,  1896. 
The  floods  of  the  Mississippi  river.    By  Wm.  Starling.    New  York,  1897. 


51 


52  LAKES. 

3.  Formation  of  deltas. 

(See  under  Lakes.) 

4.  Formation  of  bars  at  mouths  of  streams  and  estuaries. 

Two  sets  of  bars  in  streams  flowing  into  the  ocean. 
One  at  the  contact  of  stream  current  with  quiet  ocean  waters. 
Another  at  the  contact  of  the  stream  with  the  high- tide  limit. 
Shifting  of  bars  due  to  — 

a.  Varying  discharge  of  the  stream. 

b.  Storms  and  waves  at  sea. 

c.  Any  variation  of  the  currents. 

5.  Spits  formed  in  streams.* 
Deposition  by  overloaded  streams. 

An  overloaded  stream  is  one  that  receives  more  silt  than  it  can  carry, 

and  hence  cannot  keep  its  channel  open. 

In  a  sense,  parts  of  every  stream  are  overloaded  where  they  deposit. 
Such  channels  are  kept  open  by  freshets,  or  by  some  increase  of 
volume  and  current. 

Overloaded  streams  cut  no  channels,  but  fill  them  up;  they  are  constantly 
damming  up  their  own  courses  and  seeking  new  channels.    This 
leads  to  the  spreading  out  of  their  materials  as  a  broad,  flat  bed. 
Illustrations:   Southern  California,  where  streams  emerge  from  tor- 
rents of  mountains  on  the  plains ;  currents  strong  in  the  moun- 
tains, but  are  overloaded  for  the  lower  grade  of  the  plains  where 
they  deposit.    McGee  calls  this  "sheet-flood  erosion."!    It  is 
rather  a  mode  of  deposition  by  overloaded  streams. 

III.  Mechanical  Aqueous  Agencies  in  Lakes. 

Fresh-water  lakes. 

Fresh  and  salt  lakes  differ  somewhat  on  account  of  difference  in  specific 
gravities  of  water,  and  on  account  of  the  flocculation  produced  by 
the  salt  in  the  water. 

(On  flocculation  see  Mechanical  agencies  in  seas  and  oceans.) 
Coarse  silts  sink  more  rapidly  in  fresh  water,  but  fine  silts,  ow- 
ing to  flocculation,  settle  more  rapidly  in  salt  water. 
Deltas. 

Origin  and  cause. 

Illustrated  by  the  filling  of  mill-ponds  and  reservoirs  from  the  entrance 

of  the  supply  streams. 

Illustrated  by  settling-pools  on  water-supply  ditches. 
Lakes  are  all  settling  reservoirs. 

Why  the  St.  Lawrence  river  is  clear. 

Rhone  waters  flow  into  Lake  Geneva  muddy,  but  flow  out  clear  at 
Geneva;  delta  at  its  upper  end  building  constantly  outward. 

*  Tidal  sand-cusps.    By  F.  P.  Gulliver.    Science,  Nov.  22,  1895,  II,  705. 
t  W.  J.  McGee.    Bui.  Geol.  Soc.  Am.,  VIII,  87-112. 


53 


54  SEAS   AND    OCEANS. 

At  Interlaken,    Switzerland,   a    delta    formed    by    silt-laden    lateral 

streams  has  cut  the  lake  in  two. 

A  delta  deposited  at  the  mouth  of  the  Colorado  river  has  cut  off  the 
northern  end  of  the  Gulf  of  California,  and  this  northern  end 
has  evaporated. 

The  extension  of  deltas  into  lakes  turns  them  into  marshes,  and  event- 
ually into  dry  land. 

Many  of  the  marshes  and  meadows  of  the  Sierras  are  silted-up  lakes. 
Such  are  the  American  Valley,  at  Quincy;  Sierra  Valley,  and 
many  other  flat-bottomed  valleys. 
Salt-water  lakes. 

Salt  lakes  behave  like  other  bodies  of  salt  water,  except  that  they  are 

tideless,  and  consequently  produce  less  erosion. 

The  amount  of  cutting  on  shores  depends  on  the  width  of  the  play  of 
the  eroding  agent;  hence  there  is  less  on  lakes  than  on  open  seas. 
Salt  lakes  have  no  outlets;  they  lose  water  by  evaporation. 
Changes  of  level  recorded  by  the  old  shore  lines  and  deltas  about  Salt 

Lake.* 

Present  Salt  Lake  area,  2,170  square  miles;  depth,  49  feet.  Former 
area  (Lake  Bonneville),  19,570  square  miles;   depth,  1,050 
feet. 
Area  of  Lake  Erie,  9,900  square  miles;  depth,  210  feet. 

IV.  Mechanical  Aqueous  Agencies  in  Seas  and  Oceans. 
Depth. 

The  oceans  are  deeper  than  the  average  height  of  mountains. 

The  Atlantic  is  from  12,000  to  20,000  feet;    the  Pacific's  deepest  is 

27,930  feet. 

Mt.  Whitney,  Cal.,  14,898  feet;  Illimani,  22,200  feet;  Orizaba,  Mexico, 
18,314  feet;  Aconcagua,  Argentina,  23,080  feet;t  Mt.  St.  Elias, 
Alaska,  18,092  feet;  J  Himalayas,  Asia,  29,000  feet. 
Temperature. 

Challenger  map,  3>^°  south  of  the  equator  in  the  Atlantic  Ocean,  shows 
the  following  decrease  of  temperature  with  depth : 

Fahr.  Fahr. 

Surface 78        2,460  feet 39 

270  feet 68        6,600    "    37.4 

360   "    59        9,000    "    36.5 

960    "    50      12,000    "    33.7 

1,920    "    41       13,200    " 33 

The  isotherms  follow  the  contour  of  the  bottom. § 

In  many  places  the  temperature  is  below  32°  Fahr. 

Salt  water  freezes  at  27.4° ;  but  varies  with  salinity  and  pressure. 

*  Lake  Bonneville.    By  G.  K.  Gilbert.    Monograph  I,  U.  S.  Geol.  Surv. 
t  The  highest  Andes.    By  E.  A.  Fitzgerald.    29-30.    New  York,  1899. 
|  Nature,  May  3,  1900,  p.  1. 

\  The  voyage  of  the  Challenger.   By  Wyville  Thomson.    The  Atlantic.    I,  temperature 
charts.    New  York,  1878. 


55 


56  SEAS   AND   OCEANS. 


CURRENTS.* 

The  ocean's  waters  are  everywhere  in  motion. 

The  currents  flow  in  definite  channels.     Four  miles  an  hour  off  the  north- 

west coast  of  Cuba. 

Theory  of  the  causes  of  the  ocean's  currents.* 
Combination  of  — 

1.  Rotation  of  the  earth  and  lagging  waters. 

2.  Trade  winds,  that  also  lag. 

3.  Unequal  temperature  of  the  water,  producing  convection. 
Salinitv  has  been  appealed  to,  but  though  evaporation  increases  salin- 

ity, and  hence  density,  this  occurs  mostly  in  warm  regions,  and 
is  compensated  by  temperature.  Also,  there  is  a  marked  increase 
of  salinity  only  in  a  few  enclosed  places,  like  the  Mediterranean 
and  Red  seas. 
Effects  of  ocean  currents. 

Effect  on  the  distribution  of  life.\ 
Effect  on  climates. 
,         Isotherms  carried  north  and  south  on  the  surface. 

The  Gulf  Stream  carries  half  as  much  heat  from  the  tropics  as  the 

artics  get  from  the  sun. 
The  Gulf  Stream  carries  more  water  than  all  the  rivers  of  the 


Effect  on  the  North  Atlantic  and  Northwestern  Europe.  || 

Effect  on  rocks  formed  by  corals  and  other  warm-water  life-forms. 

THE  TIDES.  IT 

Tides  are  the  periodical  fluctuations  of  the  water-level  in  seas  and  oceans. 
Very  small  on  lakes.** 

At  Chicago  three  inches  at  most. 

Caused  by  moon's  and  sun's  attraction  of  the  fluid  covering  of  the  globe. 
Spring  tides  occur  when  the  two  act  together. 

Neap  tides  occur  when  these  attractions  tend  to  connteract  each  other. 
Height  in  the  open  ocean,  3  to  4  feet. 

On  shores  the  height  depends  largely  upon  shore  configuration. 

*  Les  courants  oceaniques,  leur  causes  et  leur  effets.    Par  M.  le  Major  Hennequin.    Soc. 

Beige  de  Geographic.    Bui.  4me  an.,  1880,  pp.  5-40.    Bruxelles,  1880. 
t  The  origin  of  the  Gulf  Stream.    By  P.  T.  Cleve.    Am.  Jour.  Sci  ,  April  1900,  CLIX,  310- 

311. 
The  Gulf  Stream.    By  J.  R.  Bartlett.    Bui.  Am.  Geog.  Soc.,  1881,  no.  1,  pp.  29-46;  1882, 

no.  2,  pp.  69-84. 

t  Nature,  Nov.  21,  1895,  LIII,  64-66,  534. 

Darwinism.    By  A.  R.  Wallace.    361.    London  and  New  York,  1889. 
Island  life.    By  A.  R.  Wallace.    79,262.    London,  1880. 
?  The  Atlantic.    By  Sir  C.  Wyville  Thomson.    I,  332-391.    New  York,  1878. 
|  See  H.  M.  Watts  in  Scribner's  Mo.  Mag.,  June  1902,  XXXI,  689-699. 
H  The  tides  and  kindred  phenomena  in  the  solar  system.    By.  Geo.  H.  Darwin.     Boston, 

Manual  of  tides.    By  R.  A.  Harris.    Rep.  U.  S.  Coast  and  Geodetic  Survey  for  1897,  pp. 

477—618. 
**  Nat.  Geog.  Mag.,  Sept.  1897,  VIII,  239. 


57 


58 


SEAS    AND    OCEANS. 


Puget Sound,  20  feet;  at  Chepstow,  near  Bristol,  England,  53  feet; 

Bay  of  Fundy,  70  feet.* 

Importance  of  height  due  to  the  greater  range  of  wave  action. 
Power.    Tides  have  no  erosive  power  except  in  shallow  water. 

They  keep  narrow  channels  open,t  and  increase  the  vertical  range 

of  the  work  of  waves. 

MECHANICAL  WORK  DONE  BY  SEAS  AND  OCEANS,  i 

Destructive  work  or  erosion.     The  destructive  work  (i.  e.,  erosion)  is  done  by 

waves  and  tides. 
Kinds  of  waves. 

1.  Ordinary,  or  storm  waves. 

2.  Extraordinary,  or  "tidal  waves." 

a.  Bore,  or  pororoca,  true  tidal  waves,  produced  by  submarine 

topography. 

6.  Extraordinary   waves   (improperly    called   "tidal"),   pro- 
duced by  earthquakes  or  other  submarine  disturbances. 
I.  The  destructive  work  of  ordinary  storm  waves.fy 

On  the  Bahama  Islands  blocks  of  300  cubic  feet  thrown  125  feet  on 

shore,  and  25  feet  above  high  water. || 

Work  confined  to  from  50  feet  below  to  100  to  200  feet  above  tide,  or  as 
high  as  undermining  may  affect  the  shore. 


Fig.  14.— Blow-holes  on  the  sea  coast.    Waves  catch  the  air  beneath  the  rock  shelf  in  tl 
foreground  and  force  it  out  through  two  openings. 

*  Tides  in  the  bay  of  Fundy.    Nature,  Sept.  14,  1899,  p.  461. 

On  bay  of  Fundy  tides.  Ann.  rep.  Geol.  Surv.  Canada,  new  series, VII,  1894,  pt.  M.,  14. 

t  Tidal  erosion  on  the  bay  of  Fundy.    By  G.  F.  Matthew.    Canadian  Naturalist,  new 

series,  IX,  1881,  pp.  368-373. 

I  The  sea-coast.    By  W.  H.  Wheeler.    Chaps,  i-iii.    London  and  New  York,  1902. 
?  Geikie's  Text-book  of  geology.    3d  ed.,  438,  and  references. 
I  Alex.  Agassiz.    Bui.  Mus.  Comp.  Zool.,  XXVI,  no.  1,  pp.  46,  58,  60,  66,  69,  74,  76. 


59 


60  SEAS   AND    OCEANS. 

1.  Work  below  tide. 

Violently  destructive  50  feet  below  tide,  scattering  stones  and  haul- 
ing out  by  undertow.* 

Dana  thinks  but  little  breaking  is  done  below  the  depth  bared  for 
the  plunge,  and  that  a  depth  of  20  feet  is  rarely  exceeded. 
"  Displacement  at  240  feet  is  only  a  few  inches."  t 

Scott  thinks  it  ceases  to  be  effective  "not  far  below  low-tide  mark."* 

Agitation  during  storms  to  1800  feet.§ 

Air  caught  under  ledges  and  forced  out  through  blow-holes. 

2.  Work  at  and  above  tide. 

a.  Alternate  compression  and  expansion  of  air  in  crevices  tend  to 

loosen   rock   fragments,  even  though  not  reached   by  the 
water. 

b.  Impact  of  the  water  thrown  against  the  shore. 


Fig.  15.— Notch  cut  by  the  surf  in  Ilha  Raza,  Fernando  de  Noronha  group.    (From  a 
photograph  taken  at  low  tide.) 

*  Capt.  Thos.  Dickenson's  Narritive  of  the  .  .  .  recovery  of  the  ...  treasure  sunk  in 
H.  M.  S.  Thetis,  at  Cape  Frio,  Brazil.  38,  42,  48,  59,  139.  London,  1836. 

Tidal  action  as  a  geological  cause.  By  T.  Mellard  Reade.  Proc.  Liverpool  Geol.  Soc., 
15th  session,  1873-74,  II,  50-72. 

t  Am.  Jour.  Sci.,  1885,  CXXX,  176. 

t  An  introduction  to  geology.    By  W.  B.  Scott.    119.    New  York,  1897. 

I  The  scenery  of  England.    By  Lord  Avebury.    137-138.    New  York,  1902. 

Development  of  the  profile  of  equilibrium  of  the  subaqueous  shore  terrace.  By  N.  M. 
Fenneman.  Jour.  Geol.  Jan.-Feb.  1902,  X,  1-32. 


61 


62  SEAS   AND   OCEANS. 

c.  Shingle  dashed  against  rocks  does  much  cutting.    Blocks  weigh- 

ing from  two  to  five  tons  hurled  against  the  banks ;  all  ex- 
posed shores  undercut. 

d.  Shingle  rolled  up  and  down  the  shore. 

The  grinding  sound  to  be  heard  upon  a  beach  covered  with 

loose  stones. 
Milky  color  of  water  due  to  wear. 

e.  Spray  washes  mechanically,  and  dissolves  chemically,*  some 

rocks. 
Thrown  over  island  at  Rio  de  Janeiro ;  in  the  north  of  Scotland 

lighthouse  windows  broken  at  300  feet. 
The  jagged  surfaces  sometimes  produced  by  the  solution  of  the 

shore  rocks  by  spray. 
/.    Hydrostatic  pressure  of  water  in  crevices  at  heights  of  50  to 

300  feet. 
II.   The  destructive  work  of  tidal  waves. 

1.  The  bore,  at  the  mouth  of  the  Amazon,  and  of  the  Ganges. 

Its  destruction  of  banks,  forests,  islands. 

Produced  by  topography  of  the  bottom  over  which  a  tide  wave 
trips  up.t 

2.  Extraordinary  waves  (improperly  called  tidal  waves).    Produced  by 

earthquakes  or  other  submarine  disturbances. 
Ships  left  aground  at  St.  Croix  in  1867. t 
Destruction  by  waves  during  the  Lisbon  earthquake. 
June  15,  1896,  on  the  coast  of  Japan,  175  miles  of  coast  was  struck  by 
a  wave  10  to  30  feet  high ;  some  say  80  to  100  feet.    It  killed  26,- 
975 persons;  wounded  5,390  others;  wrecked  9,313  houses,  300 
larger  and  10,000  smaller  boats,  and  destroyed  $3,000,000  worth 
of  property.      Land    washed    off,    rocks    broken,    shore    lines 
changed.     All  this  happened  in  less  than  two  minutes.    It  was 
probably  caused  by  a  submarine  volcanic  eruption  500  miles  off 
the  coast.     Pumice  was  found  floating  on  the  sea,  and  an  earth- 
quake was  felt  that  day  a  few  hours  before  the  wave.§ 
The  destructiveness  of  waves  depends  upon — 

1.  The  direction  of  the  winds,  especially  during  gales  and  storms. 

Islands  half  cut  away  off  the  west  coast  of  Ireland,  where  storms 
come  mostly  from  the  west. 

*  Alex.  Agassiz.    Bui.  Mus.  Comp.  Zool.,  XXVI,  no.  1,  pp.  48  et  seq. 

t  The  porordca,  or  bore  of  the  Amazon.   By  J.  C.  Branner.    Science,  Nov.  28,  1884,  IV,  488 

-492. 
Sur  les  mouvements  extraordinaires  de  la  mer,  etc.    Par  M.  Babinet.    Nouvelles  An- 

nales  des  Voyages,  vol.  137,  pp.  338-352.    Paris,  1853. 
Nature,  June  7,  1900,  p.  126;  Feb.  13,  1902,  p.  344;  Feb.  20,  1902,  p.  366. 
For  photograph  of  bore  see  Ann.  rep.  Geol.  Surv.  Canada.     New  ser.    VII,  1894,  part  M, 

p.  11,  plate  I. 

t  Am.  Jour.  Sci.,  XC,  133-135.    New  Haven,  1868. 
g  The  recent  earthquake  wave  on  the  coast  of  Japan.   By  Miss  Eliza  R.  Skidmore.  Nat. 

Geog.  Mag.,  VII,  Sept.  1896,  pp.  285-289,  310^312. 
Letter  of  Mabel  Loomis  Todd.    The  Nation,  July  30,  1896,  p.  84. 
Report  of  the  Krakatoa  committee  of  the  Royal  Society,  London.    93. 


63 


64 


SEAS    AND    OCEANS. 


2.  The  exposure  of  the  coast,  as  at  Santa  Cruz. 

3.  Position  of  the  bedding  planes  of  rocks,  or  structure  of  the  shore. 

4.  Character  of  the  rocks. 

Shown  by  variations  in  the  same  beds  at  Santa  Cruz. 

5.  Depth  of  the  water  off  shore. 

Deep  oceans  have  big  waves  which  break  on  shore;  shallows  cause 
them  to  break  and  form  surf  outside  before  they  reach  the 
land. 


Fig.  16. — The  sea-caves  of  the  La  Jolla  near  San  Diego,  California. 


Fig.  17.— Cathedral  Rock,  the  remnant  of  a  shore  near  San  Diego,  California,  like  the 
sea-caves  of  La  Jolla. 


65 


66 


SEAS    AND    OCEANS. 


Shore  forms  produced  by  wave  action. 

Like  destructiveness  of  the  waves,  the  forms  produced  on  shores  depend 
more  or  less  upon  — 

a.  The  direction  and  force  of  the  waves. 

b.  The  nature  and  structure  of  the  rocks. 

1.  Often  there  is  a  notch  cut  at  the  line  of  greatest  activity.* 

2.  Shelves  or  terraces  are  sometimes  cut  at  high  and  at  low  tide.   This 

can  only  occur  when  the  nature  of  the  rock  favors  it. 

3.  Caves  and  natural  arches  are  cut  where  the  variation  in  the  resist- 

ance of  the  rocks  and  the  structure  favors  them.     Portao,  Fer- 
nando de  Noronha. 


Fig. '18. — The  Portao  or  big  door,  an  opening  forty  feet  wide  cut  by  the  surf  through  an 
isthmus  of  eruptive  rocks,  Island  of  Fernando  de  Noronha. 

*  For  good  examples  of  undercut  limestone  coasts,  see  Bui.  Mus.  Comp.  Zool.,  Nov.  1900, 
XXXVIII,  plate  13. 


87 


68  SEAS   AND    OCEANS. 

4.  The  forms  are  sometimes  the  results  of  protective  agents  on  the 
rocks,  such  as  seaweeds,  millipores,  corallines,  polyps,  mollusks.* 
Passing  of  land  through  beach  condition. 
General  results  of  destructive  wave  work.     (See  p.  60.) 

CONSTRUCTIVE  MECHANICAL  WORK  OF  SEAS  AND  OCEANS,  OR  MARINE  TRANS- 
PORTATION AND  DEPOSITION. 

In  general,  transportation  and  deposition  take  place  in  seas  and  oceans 
in  obedience  to  the  laws  of  transportation ;  that  is,  the  transporting  power 
varies  with  the  sixth  power  of  the  velocity. 

Transportation  in  the  ocean  is  done  by  — 

1.  Tidal  currents. 

2.  Waves. 

3.  Undertow. 

4.  Ocean  currents. 

I.  Tidal  currents  keep  inlets  open  by  the  sweep,  or  ebb  and  flow,  of  the 

tides.t 

II.  Waves  carry  beach  materials  where  they  strike  the  beach  at  an  angle. 
They  are   most  important  where   the  wind  blows  regularly  in  one 

direction. 

Sands  and  gravels  are  carried  long  distances.      (See  this  Syllabus,  un- 
der head  of  Spits.) 

III.  The  undertow  is  the   return  oceanward  of  waters  dashed  on  shore 

as  waves;  it  is  below  the  surface. 
It  is  always  equal  to  the  influx  of  waters  on  the  surface  as  waves 

or  surf. 
It  hauls  shore-made  silts  seaward. J 

IV.  Ocean  currents  are  usually  so  far  from  the  land  that  they  carry  but 

little  sediment.      In  the  case  of  the  Amazon  river,  however,  the 
sediments  are  swept  far   north  by  the  ocean  current  and  widely 
distributed  over  the  sea  floor. 
Deposition  in  seas  and  oceans. 

Deposition  in  seas  and  oceans  takes  place  in  obedience  to  the  law  of 

transportation,  P  Oc  V6. 
Except  that 

1.  The  salt  water,  being  more  dense  than  fresh,  with  a  given  velocity, 

carries  heavier  materials,  which  lose  one-fortieth  of  their  weight. 

2.  The  salt  in  sea  water  causes  flocculation,  and  consequently  a  more 

rapid  settling  of  the  ./me  silts.     (Flocculation,  see  under  Deltas.) 
Silts  sink  in  one-fifteenth  of  the  time  required  in  fresh  water. 

*  Across  America  and  Asia.    By  R.  Pumpelly.    188.    London,  1870. 

A  visit  to  the  Bermudas.  By  Alex.  Agassiz.   Bui.  Mus.  Comp.  Zool.,  XXVI,  no.  2,  p.  245. 

Cambridge,  1895. 
t  The  action  of  waves  and  tides  on  the  movement  of  material  on  the  sea-coast.    By  W. 

H.  Wheeler.    Geol.  Mag.,  Feb.  1899,  pp.  70-71.  —  British  Assn.  Rep.,  1898. 
t  Development  of  the  profile  of  equilibrium  of  the  subaqueous  shore  terrace.    By  N.  M. 

Fenneman.    Jour.  Geol.,  Jan.-Feb.  1902,  X,  1-33. 


70 


MARINE   DEPOSITS. 


FORMS  AND  ORIGINS  OF  MECHANICAL  MARINE  SEDIMENTARY  DEPOSITS. 

Mechanical   marine  sediments,    when  deposited,   take  on   the  following 
forms : 

1.  Beaches.  4.  Sand-barrier  islands. 

2.  Spits.  5.  Submarine  banks. 

3.  Bars.  6.  Deltas. 


IRgJiWater. 


Fig.  19.^  A  section  across  a  stone  reef  or  hardened  beach,  coast  of  Brazil.    (Hartt.) 

I.  Beaches  are  of  two  kinds:  ordinary  beaches  and  storm  beaches. 

1.  Ordinary  beaches  are  of  sand,  or  other  loose  materials,  derived  from 

the  land. 

Some  materials  are  thrown  up  by  the  waves ;  some  are  drawn  sea- 
ward by  the  undertow. 
Sands  and  silts  swept  into  coves  and  bays,  accumulate  and  fill  out 

the  land. 

Dunes  often  originate  on  sandy  shores. 
Beds  on  beaches  slope  seaward. 
Sometimes  hardened  by  carbonate  of  lime. 


Fig.  20.— The  stone  reef  of  Pernambuco,  Brazil,  formed  by  the.hardening  of  a  sand 
beach. 


71 


72 


STORM   BEACHES. 


2.  Storm  beaches  are  those  thrown  up  by  storm  waves,  and  beyond  the 

reach  of  ordinary  waves. 

"  Sir  John  Coode  has  stated  as  the  result  of  his  experience  that  a 
heavy  gale  of  wind  of  twenty-four  hours  duration  would 
bring  about  far  greater  changes  in  the  conditions  of  sand- 
banks and  foreshores  than  ordinary  weather  in  twenty-four 
months."* 
They  often  dam  rivers  and  form  fresh-water  or  brackish  lakes  at 

their  mouths. 
Examples : 

Oceanside  marshes,  California. 
Lake  Merced,  near  San  Francisco. 
Lakes  on  the  Brazilian  coast. 


Fig.  21.— Cusps  on  the  beach  at  Santa  Cruz,  California. 


Fig.  22.— Diagram  illustrating  the  formation  of  beach  cusps.    The  concentric  lines 

represent  two  sets  of  wave  crests;  the  heavy  line  is  the  curve  of  a  beach 

which  with  these  waves  would  yield  cusps  of  uniform  size. 

*  W.  H.  Wheeler.    Brit.  Assn.  Rep.,  1898. 


73 


74 


SPITS    AND    BAES. 


The  form,  or  line,  of  the  beach  is  determined  partly  — 
By  wind  and  waves. 

Beach  cusps,  their  forms  and  origin.* 
By  ocean  currents. 

Cuspate  beaches  of  North  Carolina  and  South  Carolina.! 
II.  Spits.t 

Spits  are  lengthwise  extensions  of  beaches  into  the  water. 
Spits  are  formed  — 

1.  By  waves  sweeping  shingle  and  silts  into  quiet  waters  at  the 

turn  of  the  shore. § 

Examples:    Cape  Cod;   Dutch  Harbor  spit,  Anamak  Island, 
Alaska. 


Fig.  23.— Dutch  Harbor,  Anamak  Island,  Alaska,  protected  by  a  long  natural  spit. 


2.  By  conflict  between  waves  and  stream  currents. 

These  cross  the  mouths  of  streams. 
Vistula,  Baltic  Sea. 
Sea  of  Azov. 

3.  By  the  throwing  up  of  storm  beaches  on  shoals. 

These  often  connect  islands. 

Example:  St.  Paul  Island,  Pribilof  group. 
(H.  L.  Elliott's  Pribilof  Island,  p.  80.) 
They  sometimes  cause  rivers  to  flow  parallel  with  coast. 

(Gregory's  Great  rift  valley,  p.  31.) 
III.  Bars.     (Already  discussed  under  Streams,  p.  52.) 

They  are  formed  by  the  combined  action  of  streams  and  seas. 
Common  in  most  streams  flowing  into  seas. 

*  The  origin  of  beach  cusps.  By  J.  C.  Branner.    Jour.  Geol.,  Sept.-Oct.  1900,  VIII,  481-484. 

See  illustration  in  Brigham's  Text-book  of  geology,  126. 

An  example  of  wave-formed  cusp  at  Lake  George,  N.  Y.  By  F.  M.  Comstock.  Am.  Geol., 

Mar.  1900,  XXV,  192-194. 
t  Remarks  on  the  cuspate  capes  of  the  Carolina  coast.    By  Cleveland  Abbe,  Jr.    Proc. 

Boston  Soc.  Nat.  Hist.,  May  14,  1895,  XXVI,  489-497. 

J  Lake  Bonneville.  By  G.  K.  Gilbert.  Monograph  I,  U.  S.  Geol.  Surv.  Washington,  1890. 
I  Nature,  Mar.  12,  1896,  LIII,  445. 
Wave-formed  cuspate  forelands.    By  R.  S.  Tarr.    Am.  Geol.,  July  1898,  XXII,  1-12. 


75 


76  BEACHES,  BANKS  AND  DELTAS. 

IV.  Barrier  beaches. 

Long,  narrow,  and  parallel  with  the  coast. 

These  merge  into  spits  and  bars. 

Formed  by  heavy  waves  hurling  back  land  silts  along  shallow  shores.* 

Eventually  form  islands. 

Examples:  Texas,  Mexico,  Yucatan,  North  Carolina,  Baltic  Sea, 

Adriatic  Sea. 
Behind  these  barriers  the  land  gains  on  the  sea  by  the  silting  up  of 

the  lagoons. 

Examples:     Pamlico  and  Albemarle   sounds   and   the    New 
Jersey  coast. 

V.  Submarine  banks. 

Formed  wherever  silts  settle  in  the  ocean  for  a  long  time. 

Example :  off  Golden  Gate  are  the  Sacramento  Valley  sediments. 
Distinguish  between  a  submarine  bank  and  a  wave-cut  shelf. 
When  submarine  banks  come  near  the  surface  the  waves  pile  the  ma- 
terials above  the  water,  and  land  begins. 

VI.  Deltas. 

Deltas  built  in  seas  are  formed  in  the  same  general  way  as  those  in 

lakes. 

Sediments  are  brought  from  the  land  by  streams. 
Deltas  at  the  mouths  of  some  streams,  not  of  others. 
Probable  determining  causes : 

1.  Character  of  the  water  of  the  stream. 

Clear  streams  can  have  no  deltas. 
Example :  St.  Lawrence  river. 

2.  Presence  or  absence  of  marine  currents   on  the  coast,  whether 

,  ocean  or  tidal  currents. t 

At  the  mouth  of  the  Mississippi  the  tide  is  15  inches,  and  there 
are  no  ocean  currents. 

At  the  mouth  of  the  Amazon  ocean  currents  sweep  past  it, 
and  sediments  discolor  the  sea  300  miles  out. 

Rio  de  la  Plata  current  flowing  northward. 

Hoang-Ho  discolors  the  water  200  miles  from  its  mouth ;  fill- 
ing the  Gulf  of  Peleche.t 

Ganges  and  Bramapootra  have  deltas. 

Silts  probably  thrown  back  by  tides. 

History  of  the  Nile  delta. § 
General  form  of  deltas  fan-shaped. 

*  N.  S.  Shaler,  in  Physiography  of  the  U.  S.,  151-154. 

t  Marine  currents  and  river  deflection.  By  K.  A.  Daly.  Science,  June  14,  1901,  XIII,  952- 
954. 

t  Across  America  and  Asia.    By  R.  Pumpelly.    803.    London,  1870. 

I  The  physical  geology  and  geography  of  Arabia,  Petraaa,  Palestine,  and  adjoining  dis- 
tricts. By  Edward  Hull.  [London,]  1886.— See  also  Bui.  Soc.  G6ol.  de  France,  1898, 
XXVI,  558. 


lif 

ZM 


77 


78  MARINE    SEDIMENTS. 

Building  of  marine  deltas. 

Reason  of  certain  forms  in  Mississippi  delta.    They  are  the  continuation 
of  the  natural  levees.   As  the  silts  push  seaward  in  deeper  water, 
the  checking  of  the  current  is  at  the  sides  and  bottom,  so  that 
the  bottom  fills  below,  the  sides  build  up  at  the  sides,  but  the 
top  silts  are  swept  into  the  deeper  water. 
Influence  of  salt  water  on  silts.* 
Flocculation. 

Produced  by  salt,  alum,  acids,  alkalis,  cold,  heat. 

Acids  are  more  active  than  alkalis.     (Joly,  330.) 
Alum  used  to  flocculate  city  water-supply  before  filtering. 
Why  waters  containing  much  lime  are  clear. 

The  influence  of  flocculating  substances  upon  the  deposition  of  sed- 
iments brought  down  by  streams. 

Flocculation  hastens  sinking  of  fine  silts;  sediments  sink  in  one- 
fifteenth  of  the  time  required  in  fresh  water,  though  they 
lose  one-fortieth  of  their  weight. 
Rate  of  delta  growth. 

Varies  with  conditions. 

That  of  the  Mississippi,  one  mile  in  sixteen  years. 
That  of  the  Po,  twenty  miles  since  the  time  of  Augustus. 
Bay  of  San  Francisco  filling  about  the  ends. 
The  origin  of  Salton  Lake,  California. 
Delta  on  a  rising  shore. 

Example :  at  Palo  Alto,  California. 
Position  of  marine  sediments. 

Beach  deposits  slope  gently  seaward. 

Most  deposits  are  approximately  horizontal,  and  tend  to  flatten  their 

beds  by  filling  depressions. 
May  cover  larger  areas. 

Coarse  ones  near  shore,  along  a  narrow  belt,  and  nearer  their  origin. 
Fine  ones  farther  out  and  farther  from  their  source. 

*  Experiences  sur  la  sedimentation.  Par  M.  J.  Thoulet.  Annales  des  Mines.  8me  s6r., 
XIX,  5-35.  Paris,  1891. 

On  the  inner  mechanism  of  sedimentation.  By  J.  Joly.  Proc.  Roy.  Dublin  Soc.,  Nov. 
1900,  IX,  325-332. 

W.  Skey.  Chem.  News,  London,  1868,  XVH,  160;  1876,  XXXIV,  142.  —  Proc.  New  Zea- 
land Inst.,  1871,  IV,  380-382;  1878,  XI,  485-490. 

D.  Robertson.    Trans.  Geol.  Soc.  Glasgow,  IV,  257-359. 
C.  Barus.    Bui.  36,  U.  S.  Geol.  Surv. 

W.  H.  Brewer.    Nat.  Acad.  Sci.,  II,  165. 

J.  Fleming.    Trans.  Roy.  Soc.  Edin.,  1815-18,  VIII,  507. 

E.  W.  Hilgard.    Am.  Jour.  Sci.,  1873,  VI.  288,  333;  1879,  CXVII,  205. 

T.  S.  Hunt.    Chem.  and  Geol.  Essays,  10.  —  Proc.  Boston  Soc.  Nat.  Hist.,  1874,  XVI,  302. 

L.  S.  Griswold.    Ann.  rep.  Geol.  Surv.  Ark.  for  1890,  III,  192. 

H.  Leffman.    Proc.  Eng.  Club  Phila.,  1894,  XI,  293. 

G.  E.  Ladd.    Am.  Geol.,  Nov.  1898,  XXII,  282. 

H.  S.  Allen.    Nature,  July  18,  1901,  LXIV,  279-280.     (Bibliography.) 


79 


80  MECHANICAL    SEDIMENTS. 


GENERAL  CONSIDERATIONS  CONCERNING  MECHANICAL  SEDIMENTS. 

1.  The  sediments  of  streams  are  only  the  decayed  and  broken  rocks  of  the 

land. 

2.  The  ocean's  bottom  is  the  destiny  of  all  the  land. 

3.  The  rate  of  removal  depends  on  — 

a.  Topography.     (The  steeper  slopes  go  faster.) 

This  is  true  both  of  stream  erosion  and  ware  erosion,  for — 

(1)  Velocity  is  greater,  hence  transporting  power  is  greater  on 

the  steeper  land-slopes. 

(2)  On  steep  coasts  the  waves  reach  the  shore  with  greater 

force,  and  the  undermining  is  more  effective  on  account 
of  the  greater  masses  undercut. 

On  coasts  having  low  grades  the  off-shore  shallows  break 
the  force  of  the  waves  before  they  reach  the  beach. 

b.  Climate. 

Freezing  and  thawing  hasten  removal. 

c.  Structure  and  character  of  the  rocks. 

4.  Most  removal  (erosion,  or  denudation)  is  done  during  storms,  or  in  times 

of  freshets,  owing  to  the  increased  volume  and  velocity  of  streams, 
and  to  additions  from  temporary  side  streams. 

5.  Erosion  stops  at,  or  not  far  below,  the  surface  of  the  ocean. 

6.  Hence  eroded  surfaces  tell  of  a  land  condition. 

7.  The  hardening  of  a  rock  is,  in  a  sense,  an  accident. 

8.  The  laws  of  transportation  and  deposition  by  water  determine  the  dis- 

position of  the  load  of  a  current. 

9.  Thus  coarse  sediments  can  be  moved  only  by  strong  currents,  and  fine 

ones  can  be  laid  down  only  in  weak  currents. 

10.  The  nature  of  the  sediments  thus  reveals  the  nature  of  the  currents 

depositing  them. 

11.  In  an  off-shore  area — 

o.  Coarse  sediments  are  near  shore. 
6.  Finest  sediments  are  farther  out. 

c.  Coarse  sediments  are  in  lines  parallel  to  the  coast. 

d.  Finer  sediments  cover  wider  areas  than  coarse  ones. 

12.  Examine  rock  sediments  for  evidence  of  their  origin. 

13.  Water-wearing  and  water-bedding  are  done  only  by  water,  and  tell  of 

water  conditions. 


81 


82  GLACIERS. 


V.  Ice  as  a  Geologic  Agent. 

The  geologic  work  of  ice  is  done  — 

1.  In  the  mechanical  expansion  on  freezing,  whereby  rocks  are  chipped 

off  and  disintegrated,  and  earth-slopes  altered.    (Discussed  on 
p.  24.) 

2.  By  glaciers  or  ice  streams. 

3.  By  icebergs  and  floe-ice. 

GLACIERS.* 

Outline  of  glaciers  and  their  work. 

Moisture  precipitated  where  the  temperature  is  below  freezing,  falls  as 

snow. 

Snow  packs  as  ice,  and  flows  as  streams  of  ice. 
These  streams  are  called  glaciers.     (See  Plate  VII.). 
They  obey  the  law  of  flowing  streams  in  general,  so  far  as  movements 

are  concerned,  though  they  move  very  slowly. 
Debris  falling  on  the  side  of  a  glacier  is  carried  down  on  top,  or  sinks 

into  the  body  of  the  ice. 

Flowing  down  to  warmer  regions  the  ice  melts,  and  when  it  melts  more 
rapidly  than  it  is  replaced  by  snow,  the  glacier  ends  and  the  de- 
bris makes  a  moraine  or  heap,  while  the  ice,  turned  to  water, 
flows  away  heavily  charged  with  mud. 
Origin  of  glaciers. 

All  glaciers  originate  above  the  line  of  perpetual  snow.    The  line  of 
perpetual  snow  at  sea-level  is  about  the  poles;  in  passing  from 
the  poles  toward  the  equator  it  rises  higher  and  higher  above 
sea-level. 
Height  of  the  perpetual  snow  line : 

In  Switzerland,  8,500  to  9,000  feet  a.  t. 

Kites  sent  up  at  Cambridge,  Mass.,  September  19,  1897,  show  that 
the  temperature  decreased  1  degree  for  370  feet,  when  it  was 
63°  Fahr.  at  the  surface.t 

At  this  rate  the  freezing  point  would  be  at  11,470  feet. 
At  the  equator  the  freezing  point  is  at  16,000  feet  a.  t. 
In  mountainous  regions  snow  collects  as  ice  in  the  valleys. 
In  high  latitudes  (polar  regions)  it  collects  on   table-lands  and 

buries  the  topography. 
Example:  Greenland. 

*  The  great  ice  age.    By  James  Geikie.    3d  ed.    London,  1894.    (The  foot-notes  contain 

many  references.) 

Handbuch  der  Gletscherkunde.    Von  L)r.  Albert  Heim.    Stuttgart,  1885. 
The  Canadian  ice  age.    By  Sir  J.  W.  Dawson.    Montreal,  1893. 
The  forms  of  water  in  clouds  and  rivers,  ice  and  glaciers.    By  John  Tyndall.    New  York, 

1872.     (International  Science  Series.) 

The  ice  age  in  North  America.    By  G.  F.  Wright.    New  York,  1889. 
Glaciers  of  Mt.  Rainier.    By  I.  C.  Russell.    18th  aun.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  349. 
t  Science,  Oct.  8,  1897,  new  series,  VI,  562;  Oct.  22,  1897,  p.  628. 


Plate  VII. —  The  Fiescher  glacier,  in  the  Bernese  Alps,  Switzerland. 


83 


84  GLACIERS. 

Compacting  of  snow  to  ice  by  warmth  and  pressure. 
Illustrated  by  squeezing  snow. 
Blue  ice  in  tunnels. 
Hence  the  conditions  necessary  to  the  formation  of  glaciers  are — 

1.  Region  extending  above  the  perpetual  snow  line. 

2.  Abundant  precipitation. 

3.  Difference  of  temperature  to  hasten  flow. 

MOVEMENTS  OF  GLACIERS. 
Rate  of  movement. 

Swiss  glaciers  move  150  to  400  feet  per  year. 

Aar  glacier  moves  330  feet  per  year. 

Boisson  glacier  moved  210  feet  a  year  for  41  years. 

Muir  glacier  moved  7  feet  per  day,*  x  365  =  2,555  feet  per  year. 

Greenland  glaciers  move  8  feet  to  8  miles  per  year. 

Rates  vary  according  to — 

1.  The  slope  of  the  bed. 

2.  The  warmth  of  summer. 

3.  The  snowfall  or  mass  of  the  glacier  that  presses  behind. 
Method  of  determining  the  rate  of  movement. 

Transit  and  stakes. 

General  law  of  glacial  flow  is  the  same  as  that  of  streams. t 

1.  Move  more  rapidly  at  top  than  at  bottom.    (Owing  to  fricton  on 

bottom.) 

2.  Move  more  rapidly  in  middle  than  at  sides.     (Owing  to  friction 

on  sides.) 

3.  Swing  around  curves  with  the  rapid  current  on  the  outside. 

4.  Flow  more  rapidly  on  steep  slopes.     (Less  friction.) 
Explanation  of  ice  movement  (or  how  solid  matter  flows). 

Theories  offered  to  explain. i 

1.  In  1705  Scheuchzer  suggested  the  freezing  and  expansion  of 

water  in  the  cracks  in  the  ice. 

2.  Sliding  along  its  bed  by  gravity. 

This  would  work  like  a  pile  of  marbles  or  shot,  since  the  ice 
conforms  to  its  bed. 

3.  Pressure  lowers  the  freezing  point  and  makes  slush  of  the  bot- 

tom.§ 
This  probably  helps  ice  movement. 

4.  Plasticity  or  viscosity  of  the  ice  (Forbes). 

Examples  of  viscosity:  pitch,  tar,  rosin,  candy,  asphalt. 

*  Studies  of  Muir  Glacier.    By  H.  F.  Reid.    Nat.  Geog.  Mag.,  IV,  43-44.    Washington, 

1892. 

t  The  flow  of  glaciers.    W.  Upham.    Am.  Geol.,  Jan.  1896,  XVII,  16-29. 
Deely  and  Fletcher.     Geol.  Mag.,  1895,  II,  153-162. 
T.  C.  Chamberlin,  editorial  in  Jour.  Geol.,  Ill,  963-967.    Chicago,  1895. 
The  mechanics  of  glaciers.    By  H.  F.  Reid.    Jour.  Geol.,  IV,  912-928.    Chicago,  1896. 
t  Glaciers  of  North  America.    By  I.  C.  Russell.    163-189.    Boston,  1897. 
1  See  VVm.  Ludlow's  experiments,  Proc.  Eng.  Club  of  Philadelphia,  IV,  no.  2,  pp.  93-99. 

Philadelphia,  1884. 


86  GLACIERS. 

Trinidad  lake. 

But  these  substances,  though  brittle,  stretch;    ice  does  not 

stretch. 
5.  Regelation  or  refreezing  theory  of  Tyndall. 

Process  shown  by  pressure  into  various  forms,  by  cutting  with 

wire,  by  the  refreezing  of  the  small  broken  fragments. 
Glaciers  are  like  ice  fragments  in  a  mold. 
The  pressure  is  all  produced  by  gravity. 

Hence  large  glaciers  flow  faster  than  smaller  ones  on  the  same  slope. 
Glaciers  are  not  smooth  and  clean,  but  irregular  and  dirty. 
Irregularities  made  by  crevasses. 

CREVASSES. 

Crevasses  are  cracks  in  the  glacier. 
Produced  by  tension. 

1.  Where  the  ice  increases  its  slope  or  flows  over  a  ridge. 

These  ridges  may  either  cross,  or  be  parallel  with,  the  glacier. 

2.  Where  there  is  a  different  rate  of  movement  of  one  part  over  another. 

Producing  — 

a.  Transverse  lateral  crevasses. 

Transverse  lateral  crevasses  point  diagon?lly  up-stream. 

Why  they  point  up-stream  and  not  down. 

How  they  swing  down-stream  and  are  crossed  by  new  ones. 

b.  Transverse  vertical  crevasses. 

Transverse  vertical   crevasses  within   the   ice  point  up- 
stream from  the  bottom,  but  their  tops  swing  grad- 
ually down  stream. 
Principle  the  same  as  for  transverse  lateral  crevasses. 

3.  Where  the  ice  stream  widens,  as  sometimes  happens,  at  the  end 

of  the  glacier. 
Longitudinal  crevasses. 

'  1.  Where  there  is  a  longitudinal  ridge  on  the  glacier's  bed. 
2.  At  the  ends  of  spreading  glaciers. 

MORAINES.* 
Rock  fragments,  soil,  etc.,  falling  upon  the  sides  of  glaciers,  accumulate 

along  the  sides  as  the  glaciers  move  forward. 
This  material  is  called  a  lateral  moraine. 

How  and  why  debris  on  one  side  may  differ  from  that  on  the  other. 
Medial  moraines  are  formed  at  the  confluence  of  two  glaciers  by  two  lateral 

moraines  running  together. 

Sometimes  there  are  many  medial  moraines  of  many  colors. 
Baltoro  glacier,  in  Hindu  Rush,  has  fifteen  moraines  of  different  colors. 
Number  of  moraines  varies  with  the  number  of  glaciers  uniting  to  form 
the  large  one. 

*  Geschichte  der  Moranenkunde.    Von  Dr.  A.  B.  Edlen  von  Bomersheim.    Abh.  der  K.  K. 
Geog.  Gesell.  in  Wien.    Ill,  B,  no.  4.    Wien,  1901. 


87 


88  GLACIERS. 

Terminal  moraines  are  the  accumulations  of  debris  at  'the  ends  of  the  glacier 
They  are  made  of  the  lateral  and  medial  moraines,  and  of  all  the  sol: 

matter  carried  in  the  body  of  the  ice. 

Forms  of  terminal  moraines  determined  by  the  form  of  the  end  of  the  glacie 
Circular  when  the  glacier  is  lobate. 

Not  water-sorted,  but  a  heterogeneous  mixture  of  unsorted  material. 
Ground  moraine  is  the  debris,  soil,  clay,  etc.,  on  which  the  ice  sometim 

rests. 

Glacier  often  slides  over  the  moraine,  and  over  part  of  its  own  mat 
at  the  end.* 

ERRATICS  OR  GLACIAL  BOULDERS. 

Blocks  of  rock  carried  by  ice,  and  left  scattered  by  the  melting  of  the  ice 
Erratics  often  occur  in  large  numbers. 
Sometimes  they  are  of  very  large  size. 
In  Switzerland,  40  to  73  feet  long  by  20  feet  high. 
One  of  240,000  cubic  feet  is  biggest. 
The  Madison,  N.  H.,  boulder,  70,000  cubic  feet.t 

STRIDE,  t 

Strix  are  scratches  made  on  the  bed-rock  over  which  ice  moves,  or  on  i 

blocks  held  in  the  ice.    ( See  Plate  VIII,  opp.  p.  94.) 
Rock  fragments  held  in  the  grip  of  the  ice  and  pushed  forward  scrat 

the  bed-rock. 
The  striae  cut  deep  at  one  end  show  the  direction  of  the  movement 

glaciers. 
Fragments  held  in  the  ice,  ground  against  the  bottom,  are  striated  a 

faceted. 

Why  several  faces  are  worn  on  a  single  block. 

Differences  between  ice-worn,  water-worn,  and  wind-worn  pebbles. 
Why  all  glacial  pebbles  are  not  faceted. 
Some  never  reach  the  bottom  of  the  ice. 
Some  have  been  water- worn  since  they  were  grooved. 
Deep  grooves  of  stream  channels  sometimes  striated  by  ice  pressed  ii 

them. 
Polishing  is  produced  when  the  ice  is  filled  with  sand  and  fine  debris. 

THE  CROSSING  OF  STRLE.§ 
Caused  by  — 

1.  Spreading  at  the  end  of  an  ice-lobe. 

Produced  by  change  of  volume. 

2.  Increase  and  decrease  of  confluent  ice-streams. 

*  Glacier  motion  and  erosion.    By  R.  M.  Deeley.    Qeol.  Mag.,  Dec.  1898,  pp.  564-565. 

t  Crosby.    Appalachia,  VI,  61-70. 

t  For  examples,  see  University  of  the  State  of  New  York,  Sate  Museum  Report  49,  pi 

1895,  p.  324. 
I  Ann.  rep.-Geol.  Surv.  Canada,  new  ser.  VII,  pt.  M,  75-81.    Ottawa,  1895. 


89 


90  GLACIERS. 

3.  Turning  of  stones. 

4.  Bringing  of  glacier  under  local  topographic  influence. 

Difference  between  water-wearing  and  ice-wearing  of  rock  in  place.* 

GLACIAL  STREAMS. 
Superglacial  streams. 

Formed  by  the  melting  of  the  ice. 

Plunge  into  crevasses,  forming  moulins,  and  grinding  out  pot-holes. 

Lucerne  glacier  garden . 

Archbald  pot-hole. t 

Subglacial  streams  are  the  superglacial  streams  after  passing  beneath  the 
ice  through  crevasses. 

Wind  and  cut  narrow,  deep  channels  in  the  bed-rock. 

Channels  exposed  at  Grindelwald  and  Zermatt,  Switzerland. 

On  large  glaciers  they  sometimes  come  to  the  surface  again. J 

GEOLOGIC  WORK  OF  GLACIERS. 

Geologic  work  of  glaciers  is  done  as  erosion,  transportation,  and  deposition. 

I.  Erosion.^    Rock-set  ice  grinds  its  bed ;  grooves,  striae,  polish. 

Streams  cut  pot-holes,  wear  channels. 

Color  and  character  of  water ;  gletscher-milch. 
Amount  of  wear  shown  approximately  — 

1.  By  topography. 

2.  By  gletscher-milch  examination. 

3.  By  glacial  debris,  or  drift,  left  over  the  country  on  the  retreat 

of  the  ice. 

II.  Transportation.    The  materials  carried  are  either  in  the  form  of  lateral 

or  medial  moraines,  materials  scattered  through  the  ice,  or  silts 
washed  along  by  glacial  streams. 

III.  Deposition.    Glacial  deposits  are  — 

1.  Terminal  moraines. 

2.  Lateral  moraines. 

3.  Isolated  boulders. 

4.  Water  deposits. 

Between  lobes  in  pools. 

In  ice-dammed  lakes  in  their  lower  courses.  || 

*  The  rock-scorings  of  the  great  ice  age.    By  T.  C.  Chamberlin.    7th  ann.  rep.  U.  S.  Geol. 

Surv.,  1876-85.    Washington,  1888. 

Glacial  erosion.    By  W.  M.  Davis.    Proc.  Boston  Soc.  Nat.  Hist.,  1882,  XXII,  19-58. 
t  Branner.    Proc.   Am.   Phil.   Soc.,  XXIII,  353-356.    Philadelphia,  1886.    Ann.  rep.  Geol. 

Surv.  Pa.  for  1885,  pp.  615-625.    Harrisburg,  1886. 
Giants'  Kettles  near  Christiania  and  in  Lucerne.    By  W.  Upham.     Am.  Geol.,  Nov. 

1898,  XXII,  291-299. 

}  See  photograph,  Jour.  Geol.,  1896,  IV,  809. 

?  Glacier  motion  and  erosion.    By  R.  M.  Deeley.    Geol.  Mag.,  Dec.  1898,  pp.  564-565. 
The  eroding  power  of  ice.    By  J.  S.  Newberry.    Proc.  Am.  Assn.  Adv.  Sci.,  1883,  XXXII, 

200-201.— Science,  1883,  II,  330.  —  Trans.  N.  Y.  Acad.  Sci.,  1885,  III,  51-52.  —School  of 

Mines  Quarterly,  1885,  VI,  142-153.  —  Proc.  Am.  Phil.  Soc.,  1882,  XX,  91-95. 
J.  P.  Lesley.    Report  Z,  Geol.  Surv.  Pa.,  XIII-XIV;  Proc.  Am.  Phil.  Soc.,  XX, 95- 101. 
II  Climbing  iincl  exploration  in  the  KaraUorum-Himalayas.    By  W.  M.  Conway.    106-179 

London,  1894. 


91 


92 


EXISTING    GLACIERS. 


Effect  of  glaciation  on  the  topography. 
Effects  of  erosion  on  hills. 
Roches  moutonnees. 

Exceptional  cases  of  angular  rock  fronts  facing  the  ice  cur- 
rents;  caused  by  the  ice  packing  against  them,  and 
thus  preventing  erosion. 
Clearing  off  of  soil. 


Fig.  24.— Map  showing  the  lobate  forms  of  the  principal  moraines  of  the  Mississippi 
Valley  region. 

Effects  of  deposition  of  drift. 
Moraines. 

Lateral. 

Terminal. 

Interlobate. 
Erratics. 
Silts  in  old  lakes;  in  ice  pools. 

Parallel  roads  of  Glen  Roy.* 
Kettle-holes.t 

ADVANCE  AND  RETREAT  OF  EXISTING  GLACIERS. 

Evidences  of  advance  and  retreat. 

1.  Observations  of  residents;  glaciers  invade  fields  occasionally. 
Photographs  at  Grindelwald. 

*  W.  Upham.    Am.  Geol.,  May  1898.  XXI.  294. 

t  Kettles  in  glacial  lake  deltas.    By  H.   L,.  Fairchild.    Jour.  Geol.,  Sept. -Oct.  1898,  VI, 


93 


94  ANCIENT    GLACIATION. 

2.  Striae  and  drift  below  the  present  ends  of  glaciers. 

3.  Trees,  that  were  cut  off  by  ice,  below  present  glaciers.* 

4.  Difference  in  vegetation  on  old  and  newly  glaciated  surfaces.  t 
Swiss  glaciers  reached  a  maximum  about  1820;    retreated  till  1840; 

advanced  till  1850-60.     Reports  from  glaciers  in  all  parts  of  the 
world  showed  many  of  them  retreating  in  1899  ;  a  few  were  ad- 
vancing.! 
Evidence  of  the  unquestionable  origin  of  glacial  phenomena. 

Striae  on  bed-rock. 

Striae  on  boulders. 

Old  moraines;  forms;  mixing  of  material  not  water-sorted. 

Transported  blocks. 

PLEISTOCENE  OR  ANCIENT  GLACIATION. 

These  phenomena  led  to  the  discovery  of  the  former  glaciation  of  Switzerland: 

1.  Striae  down  the  valleys.     (See  Plate  VIII.) 

2.  Erratic  blocks  from  the  Alps  on  the  sides  of  the  Jura  mountains. 
Time  required  to  carry  blocks  suggests  the  length  of  the  glacial  epoch: 

1,000  to  2,000  years,  as  glaciers  now  move.     Probably  moved  faster. 
The  ice  rose  4,400  feet  on  the  Jura  mountains,  and  flowed  to  Lyons, 
France,  a  distance  of  more  than  200  miles.     Another  branch  flowed 
eastward  toward  Zurich  about  200  miles.  § 
Reluctance  rvith  which  theory  of  glacial  epoch  was  accepted. 

Extension  by  Agassiz  of  the  theory  to  England,  Scotland,  and  Ireland. 

Shown  by  topography,  drift,  and  striae. 
Extension  to  America. 
Confirmed  by  Agassiz  landing  at  Halifax,  N.  S.,  in  1846.  || 

GLACIATION  IN  NORTH  AMERICA. 

Evidences  of  glaciation  in  North  America. 

Striae,  or  furrows. 

Striated  boulders. 

Till,  or  boulder  clay. 

Moraines. 

Erratics. 
Area  of  glaciation. 

Includes  parts  of  the  Rocky  mountains  and  of  the  Sierra  Nevada  moun- 
tains. 

Driftless  area  of  Wisconsin.^ 

*  I.  C.  Russell.    13th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  63. 

t  Glacier  Bay  and  its  glaciers.    By  H.  F.  Reid.    16th  ann.  rep.  U.  S.  Geol.  Surv.,  421-461. 

Washington,  1896. 
t  The  variations  of  glaciers.    By  H.  F.  Reid.     Jour.  Geol.,  1901,  IX,  250-254,  and  earlier 

reports  there  cited. 
g  See  map  of  the  glaciers  of  Switzerland  and  France,  in  his  Equisse  g^ologique  du  ter- 

rain erratique  .  .  .  du  bassindu  Rhone.    Par  A.  Falsan.    Lyon,  1883. 
l  sketches.    By  L.  Agassiz.    II,  77.    Boston,  1886. 


The  driftless  area  of  the  upper  Mississippi.    By  T.  C.  Chamberlin  and  R.  D.  Salis- 
bury.   6th  ann.  rep.  U.  S.  Geol.  SurV.,  205-322.     Washington,  1885. 


95 


96 


ANCIENT   GLACIATION. 


Origin  of  the  ice. 

The  ice  did  not  come  from  the  north  pole,  but  from  three  principal 

centers  of  accumulation. 

The  ice  moved  southwest  up  the  St.  Lawrence  valley. 
Local  origin  of  the  ice  in  the  Rocky  mountains,  Sierras,  etc. 


Fig.  25.  -The  glaciated  area  of  North  America  (shaded)  and  the  centers  of  general 
distribution  during  the  glacial  epoch.     (Chamberlin.) 

Direction  of  ice  movements  shown  by  — 

1.  Ice  marks. 

Why  some  ice  marks  go  up-hill. 

2.  Shapes  of  terminal  moraines. 


97 


98  ANCIENT    GLACIATION. 

3.  Wearing  of  hills  on  ice- ward  side. 

4.  Distribution  of  material. 

Granites  in  Indiana  and  Illinois. 
Copper  from  Lake  Superior.* 

5.  Effect  on  drainage. 

Streams  that  flowed  toward  the  ice  source  were  dammed  up  and 

left  terraces  around  the  ancient  lake  margins. 
Some  stream  channels  were  entirely  obliterated  as  surface  features. 
Lobate  forms  of  the  ice  shown  by  — 

1.  Forms  of  terminal  moraines  and  interlobate  moraines. 

2.  Direction  of  striae. 
Thickness  of  the  ice. 

In  the  eastern  United  States  the  thickness  is  shown  on  the  mountains. 
Elk  Mountain,  northeastern  Pennsylvania,  glaciated  2,700  feet 

a.  t.,  and  1,500  feet  above  the  valley.t 
Mt.  Washington  6,000  feet  a.  t.,  boulders  on  top. 
Ice  thinned  as  the  epoch  waned,  and  finally  came  under  the  influence 

of  local  topography. 
Cross  striae  (see  p.  88). 
Retreat  of  the  ice, 

Concentric  parallel  moraines. t 
Evidence  that  the  country  was  formerly  higher  to  the  north . 

1.  The  fjord-like  bays  of  Maine.$ 

2.  Hudson  river  gorge  out  at  sea  could  only  be  made  by  subaerial  ero- 

sion. || 

3.  Preglacial  channels  of  Cuyahoga  at  Cleveland,  Ohio. 

Wells  strike  bed-rock  at  228,  333,  470,  203,  392  feet  below  Lake 

Erie  water-level  (see  p.  102). 
These  must  have  been  made  before  the  glacial  epoch,  for  they  are 

now  filled  with  glacial  drift. 

4.  Possibly  the  drowned  valleys  of  California,  Puget  Sound,  and  north, 

stood  higher  during  the  glacial  epoch  and  sank  at  its  end. IT 
Elephants'  teeth  from  St.  Paul  island,  of  the  Pribilof  group,  an 
island  about  275  miles  from  the  mainland,  and  in  a  shallow 
sea. 

5.  Terraces,  or  old  shore  lines,  around  Lake  Ontario,  show  that  that 

lake,  since  the  glacial  epoch,  has  sunk  on  the  north  more  than 
on  the  south. 
The  "  ridge  road  "  of  northern  New  York. 

*  Copper  mines  of  Isle  Royale,  Lake  Superior.  By  W.  H.  Holmes.  Am.  Anthropolo- 
gist, III,  684-696.  Washington,  1901. 

t  Branner.    Am.  Jour.  Sci.,  1886,  CXXXII,  363-366. 

t  See  maps  in  Monograph  XXXVIII  of  U.  S.  Geol.  Surv.,  and  Monograph  XXXIV,  opp. 
p.  392. 

?  Gannett.    Physiography  folio  I,  U.  S.  Geol.  Surv. 

I  Geology  of  the  sea-bottom  in  the  approaches  to  New  York  bay.  By  A.  Lindenkohl. 
Am.  Jour.  Sci..  1885,  CXXIX,  475-480. 

1i  The  submerged  valleys  of  the  coast  of  California.  By  George  Davidson.  Proc.  Cal. 
Acad.  Sci.,  I,  no.  2,  pp.  73-103.  San  Francisco,  1897. 

Drift  phenomena  of  Puget  Sound.    By  Bailey  Willis.     Bui.  Geol.  Soc.  Am.,  1898,  IX, 


99 


100 


GLACIATION    IN    NORTH    AMERICA. 


Some  of  the  results  of  glacialion  in  North  America. 
The  region  affected  varies  between  — 

1.  The  narrow  valleys  of  New  England,  New  York,  and  Pennsylvania. 
!?.  The  broad,  flat  plains  east  of  the  Rocky  Mountains. 

3.  The  basin  regions  of  the  Great  Lakes,  now  reaching  (Huron)  121  to 

492  feet  (Ontario)  below  ocean  level. 

4.  The  far  inland  Rocky  Mountain  ranges. 

n.  The  Pacific  ranges  of  the  Cascades*  and  Sierras. t 

It  is  to  be  expected  that  in  so  varied  a  region  the  influences  would  vary. 


Fig.  26. -Ice-marked  granite  near  Lake  Tahoe  above  Glen  Alpine  Springs,  California. 
(Holway.) 

Influence  of  glaciation  on — 

1.  Vegetation. 

2.  Faunas. 

3.  Drainage  and  topography. 

4.  Agriculture. 

5.  Roads. 

6.  Mining. 

7.  Architecture. 

*  Geology  of  the  Cascade  Mountains  in  northern  Washington.    By  I.  C.  Russell.    80th 

nu   a™n'  rep"  U'  S'  GeoL  Surv-'  Pt-  n-    Glaciation,  150-192 
t  The  Pleistocene  geology  of  the  south  central  Sierra  Nevada,  with  especial  reference 

°  °l  *•  W'  TUrner'    PTOC-  CaL  A 


101 


102 


INFLUENCE    OF    GLACIATION. 


I.  Influence  on  vegetation.* 

Cold  climate  crowded  vegetation  southward.    Retreating  ice  left  behind 

arctic  forms. 
Arctic  forms  left  on  mountain  tops. 

Cases  of  Mt.  Washington,  Teneriffe,  and  Java. 
Swiss  mountains  have  many  forms  that  could  only  have  come  from 
the  north  when  it  was  cold  in  the  valleys. t 

II.  Influence  on  faunas. 

Insects  left  on  Mt.  Washington. i 

They  cannot  live  in  the  valleys  now. 

Fresh-water  fishes  and  mollusks  migrated  northward  from  the  Missis- 
sippi drainage, §  and  passed  over  the  present  divides  when  the 
drainage  flowed  into  the  Mississippi. 

III.  Influence  on  topography  and  drainage. 

Moraines.    Long  Island,  N.  Y.,  largely  a  terminal  moraine  resting  on 

Cretaceous  rocks. || 

Kettle-holes  and  lakes  in  the  moraines. 

During  the  ice  age  former  streams  were  buried  and  their  channels  tilled  with 
drift  after  the  retreat;  new  channels  had  to  be  established : IT  Cuya- 
hoga  (see  p.  98),  Chicago,**  Niagara. 
New  drainage  developed  as  the  ice  melted. 

Lake  Michigan  drained  southward;  buried  channels ;tt  impossibility 
of  locating  many  of  them. 


Fig.  27.-Preglacial  topography  of  the  coal  region  of  Indiana  baried  under  glacial  drift. 
(Ashley.) 

Wabash  drainage. 

Terraces  at  Terre  Haute,  Indiana. 
Evidences  of  a  much  larger  stream. 
Floods  from  the  melting  ice. 

Proc.  Am.  Assn.  Adv.  Sci.,  1872,  XXI,  14. 


Wyoming 
647. 


as  to  the  public  water  supplies. 
.  Pierce.  Am.  Geol.,  Sept.  1897,  X 
F.  A.  Hill.  Ann.  rep.  Geol  Surv.  Pa.  for  1885,  pp.  637- 
'.  Leverett.  Monograph  XXXVUI,  U.  S.  Geol.  Surv., 
Ste  7itSChicae  ^18^°  area'  By  Ffank  Leverett-  BuL 


103 


104  INFLUENCE    OF    GLACIATION. 

Mohawk-Hudson  drainage. 

Terraces.     Origin  of  Niagara  gorge.     St.  Lawrence  drainage  last.* 
Lake  Agassiz.i 

Ponding  back  of  the  water  by  the  ice. 
Winnipeg  on  the  old  lake  bed. 
Postglacial  lakes.* 

Origin  of  glacial  lakes. 

Left  by  morainal  dams. 
Left  in  scooped-out  rock  basins. 
"  Finger  Lakes,"  of  New  York. 

The  former  northward  drainage  dammed  by  drift. § 
Glacial  lakes  of  the  Sierras. 
Donner  Lake. 
Fallen  Leaf  Lake. 

IV.  Influence  of  glaciation  on  agriculture. 

Nature  of  glacial  soils :  mixed,  pulverized,  hence  more  fertile  and  more 

valuable. 
In  Ohio  the  glacial  border  separates  the  less  productive  from  the  more 

productive  parts. 

Drift  soils  of  the  Northwest  noted  for  fertility. || 

In  the  driftless  area  of  Wisconsin  the  land  is  worth  $10  an  acre,  or  less. 
Loess  of  the  Mississippi  valley. 

Origin  from  flooded  streams?  IT 

At  Louisville,  Ky.;  St.  Louis,  Mo.;  Omaha,  Neb.;  Kansas  City,  Mo.; 

Des  Moines,  Iowa;  Vicksburg,  Miss.;  Memphis,  Tenn. 
Fine  soil. 

V.  Influence  on  roads. 

Glacial  gravels  make  good  roads. 
Roads  as  an  index  of  civilization. 

VI.  Influence  on  mining. 

Pot-holes  at  Archbald.     (See  p.  42.) 

Nanticoke  disaster.** 

Buried  river  channels.     (See  p.  102.) 

VII.  Influence  on  architecture. 

Milwaukee  cream-colored  bricks  from  glacial  clays  containing  lime. 

St.  Louis  and  Memphis  red  bricks  from  the  loess. 

At  many  places  in  the  Northwest  glacial  boulders  used  for  houses. 

*  Glacial  waters  in  the  Finger  Lake  region  of  New  York.    By  H.  L.  Fair-child.    Bui.  Geol. 

Soc.  Am.,  1899,  X,  27-68. 

t  Monograph  XXV,  U.  S.  Geol.  Surv.  — Tyrell,  Jour.  Geol.,  1895,  IV,  811-815. 
|  Ann.  rep.  Geol.  Surv.  Canada.    New  ser.,  VII,  1894,  pt.  B,  306. 
I  Glacial  lakes  in  central  New  York.    By  H.  L.  Fairchild.    Am.  Jour.  Sci.,  April  1899, 

VII,  249-263.— Bui.  Geol.  Soc.  Am.,  1893,  V.348.-F.  B.  Taylor.   Am.  Geol.,  July  1899, 

XXIV,  6-38. 

\  Geology  of  'Wisconsin.    II,  189.    Madison,  1877. 
Geology  of  Minnesota.    I,  351-385.    Minneapolis,  1884. 
«!  Origin  of  the  loess  of  the  Mississippi  valley.  T.  C.  Chamberlin.  Jour.  Geol.,  Nov.-Dec. 

1897,  V,  795-802.  — Abstract,   Am.  Geol.,  Sept.  1897,  XX,  197;    Oct.    1897,  274-275.— 

T.  O.  Mabry,  Jour.  Geol.,  1898,  VI,  273-302.  -  12th  ann.  rep.  U.  S.  Geol.  Surv.,  401-404. 

—  B.  Shimek,  Am.  Geol.,  Dec.  1901,  XXVIII,  344-358. —  Jour.  Geol.,  VII,  122-140.- 

Sardensen,  Am.  Jour.  Sci.,  CLVII,  58-60.  — Keyes,  Am.  Jour.  Sci.,  CLVI,  299. 
**  Buried  valley  .  .  .  near  Nanticoke.    Ann.  rep.  Geol.  Surv.  Pa.,  1885,  pp.  626-636.    Har- 

risburg,  1886. 


105 


106  THE   GLACIAL    EPOCH. 

OTHER  THEORIES  ADVANCED  TO  EXPLAIN  GLACIAL  PHENOMENA. 
(These  are  mentioned  as  illustrating  the  process  by  which  a  natural 
explanation  is  sought  for  natural  phenomena.) 

1.  The  deluge  of  biblical  account.* 

2.  Tipping  up  of  the  north  end  of  America,  and  the  elevation  of  the 

Alps.t 

3.  Waves  of  folding  rocks.% 

4.  Iceberg  theory. § 

5.  Destroyed  planet  and  the  tail  of  a  comet.\\ 

OBJECTIONS  FORMERLY  URGED  TO  THE  GLACIAL  THEORY. 

I.  The  striae  show  that  the  ice  moved  up-hill. 

Some  up-hill  movements  are  local. 

In  the  St.  Lawrence  valley  the  slope  has  changed  since  the  glacial 
epoch. 

II.  Present  climate  would  be  colder. 

But  5°  to  6°  lower  temperature  would  bring  the  Swiss  glaciers  to  Ge- 
neva; hence  a  very  slight  change  of  the  annual  temperature 
would  cause  a  glacial  epoch. 

III.  Agassiz's  theory  of  South  American  glaciation. 

This  theory  was  that  a  glacier  formerly  flowed   down  the  Amazon 

valley.  IT 

This  proved  too  much ;  life  would  have  been  extinct. 
This  theory  not  found  correct.** 

DATE  OF  THE  GLACIAL  EPOCH. 

Can  be  shown  by  the  geologic  work  done  since  glaciation. 

Case  of  Niagara  Falls:   estimates  range  from  3,500  years  to  hundreds  of 

thousands  of  years,  ft 
Case  of  St.  Anthony's  Falls,  Minneapolis,  about  8,000  years.it 

*  For  geological  explanation  of  the  deluge,  see  La  face  de  la  terre.  Par  E.  Suess.  25-95. 

Paris,  1897. 

t  Poggendortf's  Annalen,  1827,  IX,  575.  —  Bui.  des  Sci.  Nat.,  Mai  1828,  pp.  5-7. 
t  H.  D.  Rogers.    Am.  Jour.  Sci.,  1844,  XL VII,  274  et  seq. 
\  Acadian  geology.    By  J.  W.  Dawson.    64-73,  2d.  ed.    1868. 
I  Kruger.    Bui.  des  Sci.  Nat.  et  de  G6ol.,  Sept.  1826,  p.  6.  —  Ragnarok.    By  Ignatius 

Donelly. 
1i  Atlantic  Monthly,  July  and  August,  1866.  Geological  sketches.  By  L.  Agassiz.  II,  153. 

Boston,  1886. 
**  The  supposed  glaciation  of  Brazil.  By  J.  C.  Branner.    Jour.  Geol.,  I,  753-772.    Chicago, 

tt  Niagara  Falls  and  their  history.    By  G.  K.  Gilbert,    Physiography  of  the  United 

States,  235-236. 
Guide  to  the  geology  and  paleontology  of  Niagara  Falls  and  vicinity.  By  A.  W.  Grabau. 

Bui  N.  Y.  State  Mus.,  no.  45,  vol.  IX,  pp.  82-85.    Albany,  1901. 
U  N.  H.  Winchell.    The  geology  of  Minnesota.    Vol.  II  of  the  final  report.    313-341.    St. 


107 


108  THE    GLACIAL    EPOCH. 


LENGTH  OF  THE  GLACIAL  EPOCH.* 

Was  man  here  during  or  before  the  glacial  epoch  f 

Implements  should  be  in  the  drift  if  he  was  here. 

The  Trenton  gravels,  in  which  human  implements  have  been  found, 

are  far  south  of  the  ice  margin. t 
Minnesota. 

Stump  and  root  holes. 
Burrowing  of  animals. 
In  Europe.* 

WILL  THE  GLACIAL  EPOCH  RECUR? 

Depends  on  cause  or  causes. 

If  the  cause  recurs,  the  epoch  will. 

If  the  cause  is  astronomic,  its  return  is  to  be  expected. 
Evidences  of  interglacial  epoch. § 

Several  lignite  beds  in  the  glacial  deposits  near  Zurich,  Switzerland. 

Topographic  variation  and  difference  in  oxidation  in  Illinois,  Indiana, 
and  Yosemite  Valley  region. 

Shells  in  wrinkled  loess. 

Nature  of  marine  fossils  inter  bedded  with  drift.  || 
Evidence  of  previous  glacial  epochs.^ 

In  the  Mesozoic  rocks  of  India.** 

In  the  Carboniferous  rocks  of  India  and  South  Africa. 

In  Tertiary,  or  pre-Tertiary,  rocks  in  South  Australia,  tt 
Hence  the  glacial  epoch  may  return. 
The  conditions  move  slowly. 

CAUSES  OF  A  GLACIAL  EPOCH. 

Evidently  the  climate  must  have  been  different,  though  not  necessarily 
arctic.  In  Alaska  forests  are  growing  alongside  of  glaciers,  and  even 
in  the  moraines  upon  the  ice.ii 

*  See  F.  B.  Taylor,  Jour.  Geol.,  1897,  V,  421-465.  Makes  retreat  from  Cincinnati,  Ohio,  to 
Makinac  75,000  to  150,000  years,  and  glacial  epoch  150,000  to  300,000  years  or  more. 

W.  Upham,  Am.  Geol.,  Oct.  1897,  XX,  268. 

Geikie's  Great  ice  age.    812-815. 

t  G.  F.  Wright  and  A.  Hollick.  Science,  Oct.  29  and  Nov.  5,  1897.  —  W.  H.  Holmes.  Jour. 
Geol.,  1893,  I,  15-37  and  147.  — Science,  new  ser.,  vol.  VI,  1897. —Several  papers  in 
Proc.  Am.  Assn.  Adv.  Sci.,  1897,  XLVI,  344-390.  — F.  Russell.  Am.  Nat.,  XXXIII, 
143-153. 

t  Man  in  relation  to  the  glacial  period.  By  Dr.  H.  Hicks.  Nature,  Feb.  24,  1898,  LVII, 
402.  Nature,  Oct.  6,  1898,  p.  559. 

2  Interglacial  deposits  in  Iowa.    By  S.  Calvin.    Proc.  Iowa  Acad.  Sci.,  1898,  vol.  V. 

II  On  the  interglacial  submergence  of  Great  Britain.  By  H.  Munthe.  Bui.  Geol.  Inst. 
Univ.  of  Upsala,  1898,  III,  369-411. 

11  Neues  Jahrb.  f.  Min.,  1896,  II,  61-86,  and  plate  V.  Bibliography.  —Geol.  Mag.,  1886.  Ill, 
492-495.  —  For  bibliography,  see  Am.  Geol.  Mag.,  1889,  III,  299-330.  —  The  great  ice 
age.  By  James  Geikie.  3d  ed.,  817-826.  London,  1894.  — Am.  Geol.,  Mar.  1902, 
XXIX,  169-170.  —  Molengraaff,  in  Trans.  Geol.  Soc.  South  Africa,  IV,  pt.  V,  pp.  104- 

Geologie  de  la  Republique  Sud-Africaine  du  Transvaal.    Par  M.  G.  A.  F.  Molengraaff. 

Bui.  Soc.  G6ol.  de  France,  4me  Se~r.  I,  71-81.    Paris,  1901. 
**  C.  H.  Hitchcock.    Am.  Geol.,  April  1899,  XXIII,  252. 
n  Glaciated  boulders  at  the  base  of  the  Permo-Carboniferous,  etc.    By  T.  W.  E.  David, 

Jour,  and  Proc.  Roy.  Soc.  N.  S.  W.,  1899,  XXXIII,  154. 
U  I-  C.  Russell.     13th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  66. 


109 


HO  THE    GLACIAL   EPOCH. 

Leblanc  thinks  an  average  of  7  degrees  Centigrade  lower  than  now  would 

produce  glacial  epoch.* 

Temperature  falls  1  degree  Centigrade  for  188  metres  in  elevation. 
Snow  line  in  the  Alps  is  at  1,200  metres;  a  decrease  of  5  degrees  in  the 

temperature  of  that  region  would  bring  the  ice  down  to  260  metres, 

or  below  Geneva. 
Difference  of  temperature  may  have  been  due  to  geographic  or  astronomic 

causes. 
Suggested  geographic  causes .t 

1.  Change  of  ocean's  currents. 

2.  Change  of  trade  winds. 

3.  Elevation  of  land  above  snow  line. 

The  sea  bottom  of  Norway  was  at  least  2,600  metres  higher  than 

at  present.* 
That  northern  North  America  was  higher  is  shown  by  the  fjords 

of  Maine  and  British  Columbia  and  by  the  ice  flowing  up 

the  St.  Lawrence  valley;   Canada  was  at  least  1,200  feet 

higher  than  at  present. 

4.  Change  in  distribution  of  land  and  water. 

We  have  no  evidence  of  such  changes  during  the  glacial  epoch. 
Supposed  astronomic  causes.^ 

5.  Increase  of  the  obliquity  of  the  ecliptic. 

6.  Combined  effect  of  precession  of  equinoxes  and  of  the  eccentricity 

of  the  earth's  orbit. 

7.  Changes  in  position  of  earth's  axis. 

In  Tertiary  times  it  was  warmer  near  the  north  pole,  as  fossil 
plants  show. 

8.  The  turning  of  an  exterior  crust  over  a  fixed  core.|| 

9.  Variation  of  the  heat  radiated  by  the  sun. 

10.  Variation  of  the  temperature  of  space. 

The  planetary  system  may  pass  through  cold  and  hot  belts. 

11.  Decrease  of  the  original  heat  of  the  earth. 
We  have  to  account  for  many  glacial  epochs. 

Certainly  due  to  lowering  of  the  snow  line,  whatever  may  have  caused 
that. 

*  Bui.  Soc.  G6ol.  de  France.    ler  seYie.    XIV,  600-611.    Paris,  1843. 

t  Chamberlin.  Jour.  Geol.,  Nov.-Dec.  1899,  VII,  751-787.  —  H.  N.  Dickson.  Geog.  Jour., 
XVIII,  516-523.  London,  1901. 

t  Om  de  senglaciale  og  post-glaciale  Nivaforandruger  i  Kristianiafeltet.  Af  W.  C.  Brog- 
ger.  683.  Kristiania,  1901. 

\  Discussions  on  climate  and  cosmology.    By  James  Croll.    Edinburg,  188.V 

Climate  and  time  in  their  geological  relations.    By  James  Croll.    Edinburg,  1875. 

Island  life.    The  causes  of  glacial  epochs.    By  A.  R.  Wallace.     121-162.     London,  1880.— 

Mars  on  the  glacial  epoch.  By  P.  Lowell.  Proc.  Am.  Phil.  Soc.,  XXXIX,  641-664.  Phila- 
delphia, 1900. 

I  Sir  John  Evans.    Proc.  Roy.  Soc.     1866. 


Ill 


112  ICEBERGS. 


ICEBERGS. 

Formed  by  sea-water  lifting  the  ends  of  glaciers. 

Humboldt  glacier,  Greenland,  60  miles  across  at  the  end. 

Muir  glacier,  Alaska,  two  miles  across  at  the  end. 
Bottoms  set  with  stones  and  debris. 

Floating,  they  carry  away  this  debris  for  thousands  of  miles. 
Icebergs  melt  and  the  stones  they  carry  fall  to  the  bottom. 

Banks  of  Newfoundland. 
Stranding  of  bergs  in  shallow  water.* 

Only  one-eighth  to  one-seventh  part  of  the  ice  remains  out  of  the  water. 

Icebergs  can  ground  in  2,000  feet  of  water. 

Contorting  of  drift  by  the  dragging  of  icebergs. 

A  large  area  south  of  the  glaciers  probably  affected  by  bergs. 

FLOE-ICE. 

Work  of  the  ice  in  streams  when  the  ice  breaks  up  in  the  spring. 
Stones  and  earth  are  carried  down. 
Ice  piled  on  the  spits  of  the  Great  Lakes. 

*  Striation  by  dragging  bergs.    Chalmers,  Geol.  Surv.  Canada,  VII,    part  M,  104-106. 

Ottawa,  1895. 
Proc.  Liverpool  Geol.  Soc.,  1895,  pp.  383-386. 


113 


114  CHEMICAL    AGENCIES. 


CHEMICAL  AGENCIES. 

Under  the  head  of  Chemical  Agencies  come  the  decomposition  and  re- 
composition  of  minerals  and  rocks,  and  the  formation  of  many  of  our  most 
valuable  mineral  deposits. 

The  operations  of  chemical  agents  are,  for  the  most  part,  invisible ;  but 
the  results  of  such  operations  become  apparent  with  time. 

When  rainfalls  on  the  earth  the  water  does  either  mechanical  or  chemical 
work. 

1.  It  flows  off  over  the  surface  as  freshets  (doing  mechanical  and  chem- 

ical work),  and  returns  to  the  air  by  evaporation. 

2.  It  soaks  into  the  ground,  to  emerge  as  springs,  or  to  be  evaporated 

from  the  soil  surface  (doing  chemical  work). 

3.  It  reaches  the  sea  by  underground  channels  (doing  chemical  work). 
All  stream,  spring,  and  well  waters  contain  mineral  matter  in  solution. 

This  is  shown  by  evaporation  of  the  water. 

Mineral  matter  is  derived  from  the  rocks  passed  through. 

Many  of  these  minerals  are  considered  insoluble  in  water. 
Why  the  minerals  are  in  solution. 

The  water  is  not  simple,  pure  water. 
The  solvent  power  of  water  is  increased  by  — 

1.  Carbonic  acid  (CO2)  derived  from  the  air. 

2.  Nitric  acid  derived  from  the  air. 

Produced  by  electric  discharges. 
More  abundant  in  the  tropics. 

3.  Organic  acids  in  the  soil. 

Carbonic  acid  from  the  decay  of  plants ;  from  the  breath  of  bur- 
rowing animals. 
Humic  acids  from  the  decay  of  organic  matter.* 

4.  Increase  of  pressure  on  the  water  column,  which  increases  its  dis- 

solving power. 

5.  Increase  of  temperature,  which  increases  the  dissolving  power  with 

minerals. 

6.  Decrease  of  temperature. 
Amount  of  dissolved  matter  in  streams. 

The  streams  come  chiefly  from  springs,  and  all  spring  waters  contain 

minerals  in  solution. 
The  amount  dissolved  varies  greatly. 

*  Phillips'  Ore  deposits.    2d  ed.,  37.    London,  1896. 

On  the  geological  action  of  the  humus  acids.    By  Alexis  A.  Jnlien.    Proc.  Am.  Assn. 
Adv.  Sci.,  1879,  XXVIII,  311-410. 


115 


116  CHEMICAL    EROSION. 

No  two  streams  are  alike. 
The  same  stream  varies  from  time  to  time. 
How  the  amount  is  determined. 

Measure  of  discharge  frequently. 
Determination  of  matter  in  samples. 
Examination  of  the  Arkansas  river  water. 

Matter  in  solution  varies  from  11  to  71  grains  per  U.  S.  gallon.     Re- 
moved in  solution  in  one  day  from  13,000  to  68,000  tons;  in  the 
year  1887-88  the  total  removed  in  solution  was  6,828,350  tons. 
All  of  this  is  invisible.* 

Minerals  in  solution  mostly  salt,  gypsum,  epsom  salt,  lime  carbonate. 
Difference  between  streams. 

Due  to  rock  differences  of  the  hydraulic  basins. 

Due  to  the  nature  of  the  water  (i.  e.,  the  contained  acids). 

Streams  from  swamps  and  marshes  usually  contain  much  organic 
acid.     Tropical  streams  often  carry  much  organic  acid  on 
account  of  the  rapid  decay  of  vegetation. 
Difference  in  the  same  stream  due  to  — 

Drainage  coming  at  different  times  from  different  parts  of  the  basin, 

where  the  rocks  differ. 

Drainage  sometimes  from  underground,  sometimes  from  surface  water. 
Concentration  of  water  by  evaporation  in  dry  weather. 

EFFECTS  OF  CHEMICAL  EROSION. 

Rocks  are  minerals;  some  minerals  are  easily  soluble,  some  are  nearly  in- 
soluble, but  all  are  soluble  with  time. 
Materials  removed  are  minerals  dissolved  from  the  rocks. 
Chemical  action  results  in  the  decomposition  and  removal  of  rocks. 
The  chemical  operations  of  decomposition  and  alteration  of  roe&t  result  in  — 

1.  Soils  (residuary). 

Depth  of  rock  decay. 

2.  Kaolins  (from  feldspar). 

Nature  and  form  of  kaolin  beds. 

Only  in  region  of  feldspathic  rocks,  or  redeposited. 

3.  Clays  (largely  kaolin). 

4.  Concentration  of  some  minerals  by  the  removal  of  others. 
The  mechanical  results  of  solution  and  rock  removal. 

1.  Etching.*     Examples. 

2.  Fluting. § 

3.  Fret- work  (see  p.  28). 

4.  Caves. 

!  w0n(i£ra?h  XIP°J -U'  S'  GeoL  Surv-  for  water  of  twenty  rivers.    (Table  A.)     176. 

t  W^^ering  of  diabase  near  Chatham,  Virginia.    By.  T.  L.  Watson.    Am.  Geol.,  Aug. 

1898  XXII,  85-101.  -  Bui.  Geol.  Soc.  Am.,  XII,  9JM08. 

Van  den  Broeck.    Compt.  Rend.  Cong.  Interval  de  Geol.,  1878,  pp.  1-11.    Paris,  1880. 
Am.  Jour.  Sci.,  3d  ser.,  XXVI,  196.  -  Am.  Naturalist,  IX,  1875,  p.  471.  -  Annales  des 

mines,  7me  ser.,  VIII,  698.    Paris,  1875. 
|  Mount  Seir,  Sinai,  etc.    By  E.  Hull.    20. 
I  Branner     Bui.  Geol.  Soc.  Am.,  1896,  VII,  280.  -  Bauer.    Neues  Jahrbuch  f.  Min.     1898, 

11,  iy-«,  puite  XI. 


117 


118 


FORMATION    OF    CAVES. 


THE  FORMATION  OF  CAVES.* 

Natural  caverns  are  formed  in  four  ways : 

1.  By  the  removal  of  rock  in  solution. 

2.  By  the  underflow  of  lava  beneath  hard  crust. 

3.  By  the  mechanical  action  of  waves  on  coasts. 

4.  By  the  differential  weathering  of  cliffs. 


Fig.  28. — Ideal  section  in  a  limestone  region,  showing  the  relations  of  caves  to  sink- 
holes and  natural  arches.     (Shaler.) 

I.  Differential  solution  and  removal  of  rock,  aided  by  mechanical  wear. 

Mammoth  Cave,  Kentucky,  has  '65  to  40  miles  of  tunnels  along  which 

one  can  walk,  besides  many  miles  of  smaller  ones  along  which 

one  can  creep.     Cavern  70  to  200  feet  high. 
500  caves  in  Edmonson  county,  Ky.t 
The  limestone  regions  of  Kentucky  extend  into  Indiana,  Tennessee, 

Arkansas,  and  Missouri.     Wyandotte  cave,  Indiana ;+  Nicajack 

cave,  Tennessee;  Luray  cave,  Virginia.^ 


Fig.  29.— Plan  of  the  limestone  caves  of  Lapa  Vermelha,  State  of  Minas,  Brazil 
(Lund.) 

*  La  sp61(§ologie  on  science  des  cavernes.  Par  E.  A.  Martel.  126  pp.  Paris,  1900.  —  Mar- 
tel.  Ann.  des  Mines,  9me  ser.  X,  5-100.  Paris,  1896.  -  Stainier.  Bui.  Soc.  Beige  de 
ijeol.,  1897,  XI,  mem.  251-272. 

t  The  Mammoth  Cave  of  Kentucky.    By  H.  C.  Hovey  and  R   E  Call 
"— — _  Am.  Geol.,  Oct.  1896,  XVIII,  228. 


1st  ann.  rep.  Dept.  of  Geol.  (of 


Abstracts  of  papers  by  H.  C.  Hovej 

I  Indiana  caves  and  their  fauna.    By  W.  S.  Bla'tchley. 

Indiana),  121-175.    Indianapolis,  1897. 
Observations  on  Indiana  caves.    By  O.  C.  Farrington.    Pub.  53  Field  Columb  Mus    I 

no  8,  Geol.  Surv.    Chicago,  1901. 
g  Am.  Geol.,  Oct.  1896,  XVIII,  228. 


119 


120  FORMATION    OF   CAVES. 

Why  the  great  caves  are  in  limestone  regions. 
The  processes  of  solution  and  removal. 

Such  caves  formerly  supposed  to  be  formed  only  above  ocean-level. 
But  waters  from  the  land  discharge  beneath  the  ocean,  hence  there 
must  be  rock  removed  below  sea-level.* 

II.  By  the  underflow  of  lava  beneath  a  cooled  hard  crust. 
Method  of  formation. 

Such  caves  are  formed  only  in  volcanic  regions. 

The  lost  streams  of  volcanic  regions  in  some  cases  flow  through  these 

caverns. 
Kildii  river,  in  Iceland,  is  only  two  miles  long;  the  rest  of  it  is  below 

ground.  t 

III.  By  the  mechanical  action  of  waves  on  coast  lines.     Processes  of  the 

wave  work. 

Chemical  action  of  sea-water  often  aids  mechanical  work.t 
Caverns  made  in  this  way  seldom  go  far  into  the  rocks. 

Examples:  at  Santa  Cruz,  California;  at  Santa  Cruz  Island;  at 
Fernando  de  Noronha.    (See  Figs.  15  and  16,  pp.  60  and  62.) 

IV.  By  differential  weathering  in  cliffs. 
Processes  of  weathering. 

Why  caves  are  formed  in  one  bed  and  not  in  another. 
Uses  made  of  cliff  caverns.^ 
(See  Plate  IX.) 

BLOWING,  "BREATHING,"  AND  SUCKING  CAVES. 

Movements  of  air  due  to  varying  temperatui-es  inside  and  outside  of  the 

caverns. 

In  summer  the  inside  air  is  cooler  and  descends. 
In  winter  it  is  warmer  and  rises. 
Flows  out  of  Mammoth  Cave  at  54°  in  summer.  || 

ICE  CAVES,  if 

SINK-HOLES. 

Sink-holes  are  formed  by  the  solution  and  downward  removal  of  rocks 
at  the  surface,  or  by  the  falling  in  of  roofs  of  caves. 

*  For  instance  of  fresh  water  discharging  beneath  the  ocean,  see  Shaler  in  Bui.  Geol. 

Soc.  Am.,  1895,  VI,  155. 
t  Iceland;  its  volcanoes,  geysers,  and  glaciers.  By  Charles  S.  Forbes.   112,145-148.  Lon- 

A  summer  in  Iceland.    By  C.  W.  Paijkull.    273-274.    London,  1868. 

Kilauea,  the  home  of  Pele.    By  Wm.  Libbey.    Harper's  Mag.,  Oct.  1897,  p  719 

For  illustration  of  Hawaii  caves  see  Scott's  Introduction  to  geology  44-45 

t  See  Agassiz,  Bui.  Mus.  Comp.  Zool.,  XXVI,  no.  1,  p.  48,  and  plates. 

2  The  cliff  ruins  of  Canon  de  Chelly,  Arizona.    By  C.  Mendeleff.   16th  ann.  rep.  Bur.  Am. 

Ethnology,  79-198,  with  plates.    Washington,  1897. 
A  summer  among  cliff-dwellers.     By  T.  M.  Prudden.     Harper's  Mag.,  Sept.  1896,  XCIII, 


II  The  Mammoth  Cave  of  Kentucky.    By  Hovey  and  Call.    9;  4. 

II  The  origin  and  occurrence  of  cave  ice.     Nature,  April  19,  1900,  LXI,  591. 

Ice  caves  and  frozen  wells.    By  W.  J.  McGee.    Nat.  Geog.  Mag.,  Dec.  1901,  XII,  433-434. 


Plate  IX. —Natural  caverns  used  as  houses  by  the 

"Cliff-dwellers."    Walnut  Canon,  near 

Flagstaff,  Arizona. 


121 


122  CHEMICAL    DEPOSITION. 

Found  chiefly  in  limestone  regions. 

Due  to  solubility  of  limestone. 

Examples  found  in  the  cave  regions  of  Kentucky,  Indiana,  Tennessee, 

Virginia,  Missouri,  and  Florida.* 

Eden  Valley,  Ky.,  covers  2,000  acres  ;t  1,000  sink-holes  in  that  county. 
Ponds  made  by  puddling  clays  in  sink-holes. 
Underground  drainage  of  cave  regions. 
Mammoth  Springs. 

Why  they  fluctuate  so  little  in  volume. 
Method  of  tracing  streams  by  the  use  of  fluorescein. 

NATCRAL  ARCHES. 

I.  Formed  by  the  destruction  of  caverns. 

Natural  Bridge  of  Virginia  in  synclinal  fold. 

In  limestone  or  volcanic  regions.*     (See  Fig.  28,  p.  118.) 

II.  Formed  by  encroachment  of  sea  on  isthmus  or  peninsula. 
Examples:  Santa  Cruz,  California;  Fernando  de  Noronha. 

(See  Fig.  18,  p.  66.) 


Chemical  Deposition. 

It  has  been  shown  that  solution  is  due  to — 

1.  Acids  in  the  water  (derived  from  various  sources). 

2.  Pressure. 

3.  High  temperatures. 

4.  Low  temperatures. 

5.  Chemical  reaction. 

6.  The  solubility  of  rock-forming  minerals  under  ordinary  conditions. 
It  follows  that    if  these   causes   be   removed   the   mineral   matter  can  no 

longer  remain  in  solution,  and  must  be  deposited. 
Deposition  from  solution  takes  place — 
I.   When  the  solvent  escapes. 

Especially  true  of  carbonic  acid  gas. 

Origin  of  stalactites ;§  stalagmites;  stone  pillars. 

Frozen  cascades. 

Origin  of  spring  deposits  of  lime  (tufa  and  travertine)  by  the  escape 
of  CO2 ;  especially  when  sprayed  at  falls. 

*  Alex.  Agas'siz.    Bui.  Mus.  Comp.  Zool.,  XXVI,  215-216. 

Shaler.    Bui.  Mus.  Comp.  Zool.,  XVI,  no.  7,  pp.  144-145,  151. 

t  The  Mammoth  Cave  of  Kentucky.    By  Hovey  and  Call.    4. 

t  Natural  arches  of  Kentucky.  By  A.  M.  Miller.  Science,  June  24,  1898,  VII,  845-846, 
illustration. 

The  Natural  Bridge  of  Virginia.  By  C.  D.  Walcott.  Nat.  Geog.  Mag.,  V,  59-62.  Wash- 
ington, 1893. 

Voyage  de  Humboldt  et  Bonpland,  premiere  partie.    Atlas  pittoresque,  pp.  9-13.    Paris, 

I  Stalactites,  etc.  By  G.  P.  Merrill.  Proc.  U.  S.  Nat.  Mus.,  XVII,  77-81  (illustration). 
Washington,  1894. 


123 


124  SALT    LAKES. 

Terraced  lime  deposits.* 

Hardening  of  beach  sands  by  ocean  water  containing  CO2. 

Examples  on  the  northeast  coast  of  Brazil.     (Plates  V  and  VI, 

and  p.  70.) 
Hardening  of  dunes  of  calcareous  sands  by  CO2  from  the  air. 

II.  When  the  temperature  is  lowered. 

Hot  water  dissolves  more  mineral  matter  (except  carbonates)  than  cold. 
Hot  waters  usually  deep  seated,  and  on  approaching  the  surface  cool 

and  deposit. 

Example:  box  from  the  Comstock  mines. 
Some  hot  springs  and  geysers  deposit  tufas. 
Quicksilver  deposited  in  cool  neck  of  retort. 
When  hot  water  is  alkaline  it  dissolves  silica  and  deposits  siliceous 

sinter. t 

III.  When  the  temperature  is  raised. 
Examples :  marls  of  Michigan  and  Indiana. i 
Effect  of  heating  hard  water  in  boilers. 

IV.  When  the  pressure  decreases. 

All  underground  water  is  under  hydrostatic  pressure. 
Pressure  decreases  as  the  water  approaches  the  surface. 
Cooperates  with  lower  temperature,  in  the  case  of  waters  from  depths, 
to  help  fill  cavities  with  mineral  matter  from  depths. 

V.  When  chemical  reactions  take  place. 
Any  reaction  that  causes  precipitation. 

Examples:   oxidation  of   iron  in  solution,  and  deposition  of  bog 

iron. 
Probable  relations  to  certain  ore  deposits. 

Some  deposits  appear  to  have  been  formed  at  the  confluence  of 

underground  streams. 

VI.  When  solutions  are  allowed  to  stand  long  undisturbed. 
Examples:  geodes;  some  veins. 

VII.  When  there  is  a  concentration  of  the  water  by  evaporation. 
This  is  chiefly  a  surface  phenomenon. 

Efflorescence,  or  "alkali,"  thus  produced  (see  p.  28);  salt,  borax,  and 

alkaline  lakes  made  in  this  way. 
"Hard-pan"  sometimes  formed  by  waters  rising  toward  the  surface. § 

SALT  LAKES. 
Origin  of  the  salt  in  salt  lakes. 

1.  From  the  cutting  off  of  an  arm  of  the  sea. 

2.  By  the  concentration  of  fresh  water. 

3.  By  some  combination  of  the  two. 

*  The  origin  of  travertine  falls  and  reefs.    By  J.  C.  Branner.    Science,  Aug.  2,  1901,  XIV, 

184-185. 

t  Am.  Geol.,  Sept.  1897,  p.  165.  —  Weed.    Folio  30,  U.  S.  Geol.  Surv.,  1896. 
t  Deposits  of  calcareous  marls.    By  I.  C.  Russell.    Science,  Jan.  19,  1900,  XI,  102. 
i  The  caliche  of  southern  Arizona.    By  W.  P.  Blake.    Trans.  Am.  Inst.  Min.  Eng.,  vol. 

XXXI,  p.     .    New  York,  1901. 


125 


126  SALT    LAKES. 

I.  Cutting  off  an  arm  of  the  sea. 

Origin  of  the  salt  in  the  ocean :  it  was  all  originally  in  the  hot  rocks  of 

the  earth. 

Water  leached  it  out  and  concentrated  it  in  seas. 
Effect  of  the  separation  of  any  part  in  dry  climate. 

Examples :  salt  spray  pools  on  sea  beaches. 
Influence  of  an  arid  climate. 

Waters  of  the  Red  Sea,  and  of  Mediterranean  Sea,*  now  denser 
than  ordinary  ocean  water,  in  spite  of  the  constant  influx  of 
fresh  water. 

Cause  of  greater  density  of  waters  of  the  tropics. 
Results  of  isolation  depend  on  the  relations  of  influx  to  evaporation. 
A  salt  lake  may  wash  out  and  become  fresh. 
San  Francisco  bay,  if  cut  off,  would  wash  out. 
Sea  of  Galilee  kept  fresh  by  inflow  and  outflow  to  Dead  Sea. 
The  Caspian  Sea  was  formerly  connected  with  the  Black  Sea;  it  is 
now  isolated  and  concentrating. 

II.  Concentration  from  fresh-water  streams. 

River  waters  contain  salt,  epsom  salt,  and  carbonate  of  lime,  etc. 

Waters  flowing  from  sedimentary  rocks  all  contain  salt,  etc. 

If  such  waters  evaporate,  the  salt  is  deposited. 

If  their  basins  overflow,  the  water  remains  fresh. 

It  is  therefore  a  question  of  evaporation  or  of  aridity. 

The  western  tributaries  of  the  Paraguay  river  are  more  or  less  salty, 

because  they  flow  'from  an  arid  region. 

The  eastern  tributaries  are  fresh,  owing  to  the  greater  rainfall.t 
Salt  Lake,  Utah,  covers  2,000  square  miles;  it  formerly  covered  50,000 

square  miles,  and  was  fresh. J 

Its  waters  are  now  more  dense  than  those  of  the  ocean. 
Freshness  indicated  by  its  former  outlet.^ 
Lakes  having  outlets  are  fresh. 

III.  Combination  of  the  isolation  of  salt  water  and  the  concentration  of  fresh 

water. 

Salton  Lake,  formerly  part  of  the  Gulf  of  California,  and  since  added 
to  by  the  influx  of  fresh  water  from  the  Colorado  river.  || 

*  Double  currents  in  the  Bosphorus,  etc.   By  S.  Makaroff.   Nature,  July  13,  1899,  pp.  261- 

t  Buenos  Ayres  and  the  provinces  of  the  Rio  de  la  Plata.    By  Sir  Woodbine  Parish.    2d 

ed.,  233.    London,  1852. 
t  The  Great  Salt  Lake.    By  J.  E.  Talmage.    Scottish  Geog.  Mag.,  Dec.  1901,  XVII,  617- 

§  Monograph  I,  U.  S.  Geol.  Surv. 

I  J.  W.  Powell.    Scribner's  Mag.,  Oct.  1891,  X,  463-468. 

Salton  Lake.    By  E.  B.  Preston,    llth  ann.  rep.  State  Mineralogist  of  Cal.,  pp.  387-393. 

Sacramento,  1897. 

The  Colorado  desert.    By  D.  P.  Barrows.    Nat.  Geog.  Mag.,  Sept.  1900,  XI,  337-351. 
Lands  of  the  Colorado  delta  in  the  Salton  basin.    By  Snow,  Hilgard,  and  Shaw.    Bui. 

140,  Univ.  Cal.  Agr.  Exp.  Sta.    Sacramento,  1902. 


127 


128 


SALT    LAKES. 


"V 

*'<*    CALfFOR 


Fig.  30.— The  shaded  portion  of  the  map  shows  the  area  formerly  covered  by  the  Gulf  of 
California. 

Association  of  salt  and  gypsum  in  salt  lakes. 

Salt  can  not  be  deposited  in  the  open  sea;  sea-water  is  too  fresh. 

In  sea-water  gypsum  is  deposited  only  after  eighty  per  cent,  of  the 

water  is  evaporated,  and  salt  after  still  further  evaporation. 
Gypsum  not  soluble  in  strong  brine;  hence  it  precipitates  first.* 
In  part  of  the  Caspian  Sea  (Gulf  of  Karabougas)  gypsum  is  now  de- 
positing. 
Middle  has  beds  of  mirabilite  (Glauber  salt),  sulphate  of  soda.t 

*  Dieulafait.    Pop.  Sci.  Mo.,  Oct.  1897.          t  Eng.  and  Min.  Jour.,  Oct.  9,  1897,  LXIV,  428. 


130  ALKALINE   LAKES. 

Thickness  of  salt  beds  (maximum) : 

Syracuse,  N.  Y.,  Warsaw,  N.  Y.,  65  to  318  feet 
Kansas,*  200  feet. 
Michigan,  32  feet. 

Goderich,  Canada,  at  964  to  1,180  feet  it  is  14  to  40  feet. 
Orange  Island,  Louisiana,  1,865  feet. 
Spain,  300-400  feet  in  hills  near  Barcelona. 
Stassfurt,  Germany.t  4,794+  feet. 
Explanation  of  great  thickness  of  salt  beds. 

Influx  of  sea-water  at  high  tide  and  during  storms. 

Examples :  Lag6a  de  Freitas,  Rio  de  Janeiro. 
Influx  due  to  evaporation  in  shallow  marginal  pools.* 
Interpretation  of  gypsum  and  salt  beds. 

Indicate  salt  lakes  and  arid  climates  at  those  places  at  the  time  of 
their  deposition. 

ALKALINE  LAKES. 

Alkaline  lakes  have  been  formed  by  the  concentration  by  evaporation  of 
waters  flowing  over  igneous  rocks  (in  which  alkaline  carbonates  pre- 
dominate). 
Mono  Lake,  California;^  area  87  square  miles  in  1887,  but  varying. 

Strong  solution  of  salt  and  carbonate  of  soda  (42.53  per  cent,  of  the  total 

constituents). 

Carbonate  of  lime,  and  borate  of  soda. 
Old  shore  line  680  feet  above  water  (higher  in  glacial  epoch),  and 

hydrographic  basin  of  7,000  square  miles. 
Region  arid  mostly;  the  minerals  will  precipitate  soon. 
Owen's  Lake,  California. 

Water  used  to  manufacture  soda. 

BITTER  LAKES. 

Bitter  lakes  are  a  further  concentration  of  salt  lakes. 
Those  containing  bittern,  or  liquor,  left  after  the  deposition  of  salt. 
Contain  Epsom  salts,  Glauber  salt. 
Such  lakes  cut  on  Suez  canal. 

They  were  below  the  level  of  the  Red  Sea. 
The  Dead  Sea  is  a  bitter  lake. 

BORAX  LAKES. 

Borax  lakes  are  formed  by  the  concentration  of  waters  flowing  from  igne- 
ous rocks  containing  borax  minerals. 
Borax  now  made  from  the  water  of  wells  sunk  in  basins. 

This  water  has  flowed  from  igneous  rocks,  and  has  been  concentrated 
in  lakes  now  dried  up. 

*  Gypsum  deposits  in  Kansas.    Am.  Geol.,  Oct.  1896,  XVIII,  236. 

t  The  salt  deposits  of  Stassfurt.    By  H.  M.  Cadell.    Trans.  Edin.  Geol.  Soc.,  V,  pt.  I,  93. 
Edinburg,  1885.  —  The  theory  of  the  Stassfurt  salt  deposits.    Nature,  Feb.  16,  1899, 

t  Karamania,  or  .   .  .  the  south  coast  of  Asia  Minor.    By  F.  Beaufort.   2d  ed.,  283.    Lon- 
don, 1818. 

?  8th  ann.  rep.  U.  S.  Geol.  Surv.,  287-299.    Bui.  60,  U.  S.  Geol.  Surv. 
Russell's  Lakes  of  North  America.    83-89. 


131 


132  PENETRATION. 

Resume.— The  matter  of  chief  geologic  importance  regarding  all  lakes, 
and  other  bodies  of  mineral  waters,  is  that  their  mineral  contents  have 
been  dissolved  from  the  rocks  over  and  through  which  they  have  passed, 
and  that  the  nature  of  their  contents  must  vary  with  the  nature  of  the 
rocks. 

THE  DEPTH  TO  WHICH  WATERS  PENETRATE  THE  EARTH'S  CRUST. 
Depth  to  which  waters  penetrate  suggested  by — 

I.  Hot  waters. 

Earth's  temperature  increases  downward. 
Not  uniform;  varies  with  crust  and  place. 

Average  about  1  degree  for  50  feet  in  depth  below  constant  line. 
Reasoning  from  temperatures  of  hot  springs. 

Thermal  Springs  of  Bath,  England,  120°  Fahr. 

If  surface  temperature  of  water  were  40°,  the  additional  80° 

would  be  had  at  80  X  50  feet  =  4,000  feet. 
Hot  Springs  of  Arkansas,  temperature: 

142° 
—  40°  temperature  at  surface. 

102°  above  normal  temperature. 

102  X  50  feet  =  5,100  feet,  depth  from  which  the  water  would 
have  come  if  the  conditions  were  average. 

II.  Depth  to  which  rocks  are  altered  by  decay. 

Suggests  the  depth  to  which  surface  waters  penetrate. 

In  Brazil,  cuts  of  100  feet;  drill  holes,  393  feet;  mines,  400  feet.* 
Certain  minerals  (iron  and  copper  sulphides)  susceptible  of  change 

to  carbonates,  oxides,  etc. 

In  mines  some  are  found  changed  to  depths  of  600,  1,000,  and  1,500 
feet.t    In  some  of  the  mines  of  West  Australia  the  rocks  and 
ores  are  altered  to  a  depth  of  400  feet.t 
These  changes  are  produced  by  surface  waters. 

GENERAL  RESULTS. 

1.  Meteoric  waters  dissolve  rocks  in  one  place  and  deposit  them  in  another, 

or  carry  them  to  the  sea. 

2.  They  remove  the  more  soluble,  and  leave  the  less  soluble. 

3.  They  form  cavities,  caves,  sink-holes,  and  channels. 

4.  These  waters  deposit  their  dissolved  materials  in  crevices  and  veins, 

and  form  surface  accumulations. 

*  Branner.    Bui.  Geol.  Soc.  Am. ,  VII,  255.  f  Penrose.    Jour.  Geol.,  1894,  II,  295. 

t  H.  C.  Hoover.    Trans.  Am.  Inst.  Min.  Eng.,  XXVIII,  758-765.    New  York,  1898. 


133 


134 


135 


136  THE    INTERIOR    OF    THE    EARTH. 


IGNEOUS  AGENCIES,  OR  HIGH  TEMPERATURES. 


The  Interior  of  the  Earth. 

Evidences  of  the  heated  condition  of  the  earth's  interior. 

1.  Downward  increase  of  temperature  in  wells  and  mines. 

(See  page  138.) 

2.  Volcanoes  with  their  accompanying  phenomena. 

Explosions,  steam,  hot  vapors  and  gases,  molten  rocks. 

3.  Geysers  and  other  hot  springs,  bringing  high  temperatures  to  sur- 

face. 

4.  Positions  and  characters  of  certain  rocks,  such  as  dikes  and  lava 

sheets,  which  appear  to  have  been  fused,  and  to  be  connected 

with  masses  penetrating  the  earth's  crust. 
Influence  of  interior  heat  on  climate. 

Not  felt  now ;  in  one  year  would  not  melt  1  mm.  of  ice  over  the  globe. 
Its  influence  felt  only  during  the  early  history  of  the  earth. 

THEORIES  CONCERNING  THE  INTERIOR  CONDITION  OF  THE  EARTH. 

I.  Fluid  molten  interior,  with  hard  crust. 

Reasons  for  the  theory. 

Outflow  of  lavas  and  hot  waters ;  high  temperatures. 
Objections  to  the  theory. 

Physicists  show  that  there  would  be  tides  in  such  a  globe. 

It  does  not  behave  like  a  molten  globe. 

II.  Solid  crust  and  center  and  molten  layer  between. 

Would  answer  geologic  conditions  unless  affected  by  tides. 

III.  Solid  as  a  globe  of  glass  or  steel. 

Because  of  behavior. 
Objections. 

Evidences  of  elevation  and  depression. 

Our  sedimentary  rocks  here  are  marine,  including  those  in 
the  mountain  tops. 

IV.  Solid  throughout,  except  local  pockets  of  molten  rocks. 
Physicists  and  geologists  can  agree  on  this.* 

Rate  of  increase  of  temperature  downward. 

Temperature  of  the  ground  surface  varies  daily  and  yearly. 
This  variation  is  due  to  outside,  or  solar,  influence. 

*  Earth  movements.    By  C.  R.  Van  Hise.   Trans.  Wis.  Acad.  Sci.,  XI,  475,  on  "  Condition 
of  the  interior  of  the  earth."    Madison,  1898. 


137 


138  THE    INTERIOR    OF    THE    EARTH. 

Level  of  no  change  in  the  tropics  is  about  4  feet  deep ;  at  New  York  it  is 

about  50  feet  deep. 
Further  north  it  is  deeper. 
Difference  due  to  climatic  fluctuations. 
Below  the  line  of  uniformity  the  temperature  rises. 
The  increase  is  constant,  but  the  rate  varies  at  different  places,  and  at  different 

depths. 

On  volcanic  cones  the  high  temperature  is  near  the  surface. 
Comstock  Lode,  Yellow  Jacket  mine.* 

1°  for  every  28  feet,  down  to  3,000  feet. 
Artesian  wells  increase  1°  for  about  50  feet. 

North  of  England,  1°  for  49  feet.t    Committee  of  the  British  Associa- 
tion prefers  64  feet  for  1°.J 
New  South  Wales,  1°  for  80  feet.t 

Schladebach  hole,  near  Leipzig,  6,560  feet,  1°  to  56+  feet. 
Idaho-Maryland  mine,  Grass  Valley,  California,  1°  to  107  feet.§ 
Wheeling,  West  Virginia,  5,386  feet,  Feb.  1897,  1°  to  80-90  feet  in  the 

upper  half;  1°  to  60  feet  in  the  lower  half.|| 
Calumet  and  Hecla  copper  mines,  Michigan,  1°  to  224  feet,  to  a  depth 

of  4,700  feet. If 

In  Dakotas  varying  from  17}^  to  45  feet  to  a  degree.** 
Variations  may  be  due — 

1.  To  varying  conductivity  of  the  rocks  (which  are  not  everywhere  the 

same). 

2.  To  varying  conditions  that  produce  high  temperatures. tt 
Temperature  of  3,000°  would  fuse  rocks. 

3,000 

50  feet  descent  for  each  degree. 

150,000  feet  =  nearly  30  miles,  the  depth  at  which  a  temperature  of 

3,000°  would  be  reached  at  this  rate. 

But  30  miles  of  rock  increases  pressure  greatly,  and  raises  the  fusing  point. 
Rocks  expand  on  fusion. 
Greater  depth  is  therefore  required  to  fuse  them. 

But  this  depth  increases  the  pressure  and  raises  fusing  point. 
Difficulty  of  reasoning  on  the  interior  conditions  of  the  earth. 
We  can  not  reproduce  the  conditions. 
Possibility  of  error  regarding  such  temperatures  and  pressures. 

*  Becker.    Monograph  III,  U.  S.  Geol.  Surv.,  229.    Washington,  1882. 

t  Nature,  1896,  LIV,  137. 

1  Reports  British  Association.     1882,  pp.  72-90. 

I  Lindgren.     17th  ann.  rep.  U.  S  Geol.  Surv.,  1896,  II,  171. 

II  Am.  Jour.  Sci.,  1892,  CXLIII,  231.  —  School  of  Mines  Quar.,  Jan.  1897,  XVIII,  148-153. 

H  Am.  Jour.  Sci.,  1895,  CL,  503.  —  The  geothermal  gradient  in  Michigan.    By  A.  C.  Lane. 

Am.  Jour.  Sci..  June  1900,  CLIX,  434-438. 
**  Geothermal  data,  etc.    By  N.  H.  Darton.    Am.  Jour.  Sci.,  CLV,  161-168. .  New  Haven, 

1898. 
1t  Sollas  suggests  (Geol.  Mag.,  Nov.  1901,  p  502)  that  the  irregular  downward  increase  of 

temperature  may  be  due  to  the  irregular  distribution  of  molten  rock  below.    This 

can  be  of  but  little  importance,  because  many  rocks  are  quite  as  hot  as  some 

molten  on.es,  but  owing  to  pressure  are  hard. 


139 


140  VOLCANOES. 

Possibility  of  fusion  being  due  to  local  relief  of  pressure,  as  in  the  case  of  the 

steam  of  geysers. 

Lava  supposed  to  come  from  a  depth  of  less  than  30  miles.* 
Ridging  of  the  crust  by  contraction  of  the  globe. 

Pressure  at  six  miles  makes  rocks  plastic  and  closes  cavities. t 
Volcanic  activity  is  mostly  confined  to  regions  of  breaking,  slipping, 

faulting,  and  thrust. 

In  any  case  the  igneous,  or  high  temperature,  phenomena  are  mostly  deep 
seated,  though  they  manifest  themselves  at  the  surface. 


Volcanoes  and  Their  Geologic  Work.} 

Volcanoes  may  be  classified  as  — 

1.  Active.  t 

2.  Dormant,  or  extinct. 

The  periodicity  of  volcanoes  is  so  irregular  and  uncertain  that  such  a 
classification  is  quite  arbitrary.  Dormant,  and  even  extinct,  vol- 
canoes become,  or  are  liable  to  become,  active. 

I.  ACTIVE  VOLCANOES. 

Definition. — A  volcano  is  usually  a  conical  hill  or  mountain,  with  an 
opening  (one  or  more)  through  which  molten  rocks,  gases,  and  cinders 
escape  from  the  hot  interior  to  the  surface.  The  mountain  is  the  result, 
not  the  cause,  and  is  not  an  essential  part  of  a  volcano. 

ERUPTIONS. 
I.  Conditions  of  eruptions. 

Eruptions  are  supposed  to  be  more  or  less  affected  by  barometric  pres- 
sure. This  could  occur  only  when  the  eruption  was  on  the  point 
of  taking  place. 

*  J.  L.  Lobley.    Geol.  Mag.,  April  1897,  p.  189. 

t  Flow  and  fracture  of  rocks  as  related  to  structure.  By  L.  M.  Hoskins.  16th  ann.  rep. 
U.  S.  Geol.  Surv.,  859.  —  C.  R.  Van  Hise.  Same  vol.,  593.  Washington,  1896. 

I  Volcanoes:  what  they  are  and  what  they  teach.    By  J.  W.  Judd.    New  York,  1895. 

Volcanoes  of  North  America.    By  I.  C.  Russell.    New  York,  1897. 

Characteristics  of  volcanoes.    By  J.  D.  Dana.    New  York,  1891. 

The  eruption  of  Krakatoa  and  subsequent  phenomena.  Report  of  the  Krakatoa  commit- 
tee of  the  Royal  Society.  Edited  by  G.  J.  Symons.  London,  1888. 

The  South  Italian  volcanoes.  By  H.  J.  Johnston-Lavis.  Naples,  1891  (With  bibliog- 
raphy.) 

The  geology  and  extinct  volcanoes  of  Central  France.    By  G.  Poulett  Scrope.    London, 

Aspects  of  the  earth.    By  N.  S.  Shaler.    46-97.    New  York,  1889. 

Volcanoes,  the  character  of  their  phenomena.    By  G.  P.  Scrope.    London,  1862. 

I. a  face  de  la  terre.    Par  E.  Suess.    Tome  I,  185-223.    Paris,  1897. 

The  ancient  volcanoes  of  Great  Britain.   By  Sir  Archibald  Geikie.  2  vols.   London.  1897. 

The  volcanoes  of  Japan.    By  John  Milne.    Trans.  Seismological  Soc.  of  Japan,  IX,  pt. 

II.    Yokohama  (1886). 

Les  volcans  et  les  tremblements  de  terre.    Par  K.  Fuchs.    6me  ed.    Paris,  1895. 
Volcanoes:  their  structure  and  significance.    By  T.  G.  Bonney.    The  Science  Series. 

London  and  New  York,  1899. 
Dutton.    4th  ann.  rep.  U.  S.  Geol.  Surv.  —  Hitchcock.    Bui.  Geol.  Soc.  Am.,  1900,  XI, 

15-60.  —  Hurlburt.    Bui.  Am.  Geog  Soc.,  XIX,  233-253.    1887. 


141 


142  ACTIVE    VOLCANOES. 

Lava  is  brought  to  the  surface  by  gravity,  or  the  difference  between 
the  weight  of  the  lava  and  that  of  the  overlying  rocks.  The  flow- 
stops  when  equilibrium  is  again  established. 

II.  Periodicity. 

Stromboli,  once  in  4  to  10  months. 
Kilauea,  in  Hawaii,  once  in  8  to  9  years. 

III.  Sequence  of  events. 
Rumbling. 
Earthquakes. 

Rumblings  and  earthquakes  are  frequent  in  many  volcanic  regions, 

and  do  not  necessarily  indicate  an  approaching  eruption. 
Vapors. 
Explosions. 
Rise  of  lavas. 
Overflow. 

IV.  Phenomena  accompanying  eruptions. 
Lava  flows  quietly  when  dry. 
Sheets  on  slopes,  or  in  valleys. 

Cones  of  lava,  or  lava  and  "  ashes,"  or  cinders. 
Lava  breaks  through  fissures  on  sides ;  due  to  hydrostatic  pressure. 
Pressure  on  the  sides  when  the  craters  are  high. 
Height  of  South  American  craters. 

Cotopaxi,  19,613  feet.*    The  following  have  long  been  extinct: 
Chimborazo,  20,498  feet;    Antisana,  19,335  feet;   Cay- 
ambe,  19,186  feet. 
When  the  rocks  contain  much  water  the  eruptions  are  explosive  and 

scatter  cinders  and  blocks. t 
Gases.* 
Earthquakes. 
Geysers. 
Elevations. 

Jorullo,  a  volcanic  peak  in  Mexico,  rose  513  metres  in  a  night  (Sep- 
tember 29,  1759). § 
Depressions. 

V.  Materials  of  volcanic  eruptions. 

1.  Lavas  and  lava  streams.  || 

Rate  of  flow  depends  partly  on  slope  and  partly  on  the  fluidity  of 
the  lava. 

*  Travels  amongst  the  great  Andes  of  the  Equator.  By  Edward  Whymper.  126-127,  342- 
New  York,  1892. 

t  Verrill.  Science,  May  23,  1902,  p.  824.  —  Verrill.  Am.  Jour.  Sci.,  XIV,  72-74,  July  1902. 
—  Gordon.  Science,  June  27,  p  1033-1034. 

t  Observations  on  Mt.  Vesuvius,  etc.  By  Sir  William  Hamilton.  164-167,118-119.  Lon- 
don, 1774. 

Santorin  et  ses  eruptions.    Par  F.  Fouque'     225  232 

A  description  of  active  and  extinct  volcanoes.    By  Charles  Daubeny.    160,  375.    London. 

Death  Gulch,  a  natural  bear  trap.    By  T.  A.  Jaggar,  Jr.    Pop.  Sci.  Mo.,  Feb.  1899,  I.IV, 

475-481.  -  Ward.    Science,  Mar.  24,  1899,  p.  459. 

?  Vues  des  Cordilleres,  etc.    Par  A.  de  Humboldt.    242-244.    Paris,  1810. 
I  Kilauea,  the  home  of  Pele.  By  W.  Libbey.  Harper's  Mag.,  Oct.  1897,  vol.  95,  pp.  714-723. 


143 


144  ACTIVE    VOLCANOES. 

Size  and  shape  of  streams.* 

Temperature. 

Effect  on  drainage. 

Dams  causing  lakes  and  diverting  streams. t 
The  topography  is  sometimes  overwhelmed.* 
The  great  lava  floods  of  the  northwestern  United  States  cover  an 

area  of  150,000  square  miles. 
Formation  of  cavea  with  striated  sides. 

2.  Fragmental  ejectamenta. 

Composition  of  the  dust  and  "smoke,"  "sand,"  and  "  ashes. "§ 
Some  ascend  20,000  feet,||  and  even  164,000  feet  in  the  case 
of  the  very  fine  dust  of  Krakatoa. 
Lapilli. 

Tuff\i  deposited  in  water. 
Pumice  in  windrows. If 
Blocks  and  other  fragments  blown  from  throat. 

Thrown  12  miles.** 
Bombs. 

Mud  produced  by  rains  in  ashes;  by  melting  ice  on  high  peaks. tt 
Burying  of  Pompeii  and    Herculaneum  under  showers  of  frag- 

mental  material ;  Herculaneum  70  to  112  feet  deep. it 
Destruction  of  St.  Pierre,  Martinique,  May  8,  1902.§§ 

3.  Inclusions. 

Brought  up  from  below. 
Show  relative  age  of  eruptions. 

4.  Gases,  steam.^ 

Volcanic  peaks  (of  construction)  built  up  by  ejectamenta. 

Largest  volcanoes  are  those  of  the  Andes,  17,000  to  19,000  feet  high. 

Aconcagua,  the  highest  peak  of  South  America,  23,080  feet,  is  of 

volcanic  rock.|||| 
Orizaba,  Mexico,  18,314  feet.     (See  Around  the  world,  opp.  p.  24.) 

*  A  summer  in  Iceland.     By  C.  W.  Paijkull.    341.    London,  1868. 

The  Bolivian  Andes.    By  Sir  Martin  Conway.    338,  and  plate.    New  York  and  London, 

t  Observations  on  Mt.  Vesuvius,  etc.    By  Sir  W.  Hamilton.    12,  foot-note.    London,  1774. 

See  Lindgren,  in  Truckee  folio,  U.  S.  Geol.  Surv.,  6. 

t  Cadell,  on  New  Zealand  volcanic  zone.    Trans.  Edin.  Geol.  Soc.,  1897,  VII,  183. 

2  Diller  and  Steiger.    On  dust  from  Martinique,  etc.    Science,  June  13,  1902,  p.  947. 

I  Whymper.    Travels  amongst  the  great  Andes.     125,  141,  326-328,  330. 

Report  of  the  Krakatoa  committee  of  the  Royal  Society,  375,  379,  282. 

H  J.  P.  Iddings.    Science,  Feb.  8,  1884,  III,  144. 

Across  Vatna  Jokul.    By  W.  L.  Watts.     105-108,  160.    London,  1876. 

**  Hamilton's  observations.    49,  note. 

tt  Travels  amongst  the  great  Andes  of  the  Equator.  By  Edward  Whymper.  126-127. 
New  York,  1892. 

U  On  ashes  about  Vesuvius,  see  Observation  on  Mt.  Vesuvius,  etc.  By  Sir  Wm.  Hamil- 
ton. 34,  note;  46,  94-95,  116.  London,  1774. 

Pompeii,  its  life  and  art.    By  August  Mau.    Translated  by  F.  W.  Kelsey.    New  York, 

??  J.  Milne.   Nature,  May  15,  1902,  LXVI,  56-58;  May  29, 1902,  LXVI,  107-112;  June  12,  1902, 

LXVf,  151-155;  June  19,  1902.  LXVI,  178-181.  —  See  also  references  under  foot-note  t 

on  p.  142. 

The  Antillean  volcanoes.    By  W.  J.  McGee.    Pop.  Sci.  Mo.,  July  1902,  LXI,  272-281. 
For  a  full  account  of  the  recent  Martinique  and  St.  Vincent  eruptions  see  articles  by  R. 

T.  Hill  and  I.  C.  Russell,  Nat.  Geog.  Mag.,  XTII,  July  1902.  -  Century   Mag.,  July 

1902,  pp.  473-483. 
||  The  highest  Andes-    By  E.  A.  Fitzgerald.    New  York.  1899.    Charts. 


145 


146 


PEAKS    AND    CONES. 


Fig.  31.— The  cinder  cone  and  lava  field  of  the  Lassen  Peak  district,  California.  (Diller.) 

Ash  and  cinder  peaks  are  steeper  than  Java  cones  (except  locally). 

The  angle  of  repose  of  dry  sand  is  40°;  of  gravel  is  35°  to  38°. 

Mt.  Hood,  Oregon,  11,225  feet;  Columbia  river  cuts  4,000  feet  in  its 
lava. 

Mt.  Tacoma,  or  Rainier  (14,449  feet). 

Mt.  Shasta  (14,440  feet)  and  vicinity. 

Volcanic  region  between  Lassen  Peak  and  Mt.  Shasta. 
Lava  cone*  are  not  so  steep. 

Angle  of  the  slope  of  Mauna  Loa. 


Fig.  32.— The  cinder  cone  of  the  Lassen  Peak  district,  California.   (Diller.) 


147 


148 


SUBMARINE    VOLCANOES. 


VOLCANIC  ROCKS. 
Lavas,  mostly  dark  colored. 

On  decay  they  often  turn  red,  rusty  brown,  a  purplish  red,  terra  rocha. 

Some  are  glassy,  like  obsidian. 

Some  "blistered"  in  appearance. 

Small,  angular,  or  rounded  fragments. 

Inclusions  among  ejectamenta. 

Some  lavas  cool  in  columns,  commonly  hexagonal,  called  basaltic. 

Examples  at  the  Columns  and  at  the  Stone  Crusher  near  Stanford 

University,  Giant's  Causeway.     (See  Plate  XI.) 
(For  the  explanation  of  the  forms  of  basaltic  columns  see  Part  III 
of  this  Syllabus. 


Fig.  33. — Horizontal  basaltic  columns  on  the  island  of  Fernando  de  Noronha. 

SUBMARINE  VOLCANOES.* 

Peaks  all  over  the  sea  bottom,  and  many  volcanic  islands,  lead  us  to  sup- 
pose that  many  of  them  have  been  made  by  submarine  eruptions. 

*  Ueber  submarine  Erdbeben  u.  Eruptionen.    Inaug.  Diss.  von  E  Rudolph.    Stuttgart, 

1887. 
On  the  geological  investigation  of  submarine  rocks.    By  J.  Joly.    Sci.  Proc.  Roy.  Dublin 

Soc.,  VIII,  509-514.    Dublin,  1898. 


149 


150  VOLCANIC    ACTIVITY. 

Submarine  lavas  are  the  same  as  terrestrial  ones.* 

Santorin  and  Theresia  Islands,  in  Grecian  Archipelago,  rose  from  the  st-a 
237  B.  C.  (Sir  Wm.  Hamilton,  158-9;  Daubeny,  L'29).     One  of  the 
Azores  near  St.  Michael  in  1628  (Sir  Wm.  Hamilton,  159). 
In  1783  one  (Nyoe)  6  or  8  miles  off  Iceland  (Forbes,  286).     Island  a  mile  in 
circumference,  washed  away  and  only  a  shoal  in  less  than  one  year. 
(Daubeny,  224.) 
In  1831  Graham's  Island,  Sicily,t  200  feet  high  (a.  t.),  and  800  feet  above 

bottom,  three  miles  around.     Active  three  weeks. 
Demolished  in  two  years. 
Bogoslof  island  in  Behring  sea.} 
Volcanic  islands,  all  deeply  wave-cut. 
St.  Helena  cliffs,  1,000  to  2,000  feet. 
Teneriffe,  Fernando  de  Noronha. 

Subaqueous  volcanoes  on  a  small   scale  sometimes   produce   "mud  vol- 
canoes.'^ 

DISTRIBUTION  OF  VOLCANOES. 

By  sides  of  deepest  and  largest  oceans. 

Wallace  suggests  that  they  "take  away  the  foundations  of  the  sur- 
rounding district,"  and  thus  make  the  neighboring  seas  deep.|| 
The  distribution  of  certain  volcanic  phenomena  are  simulated  by  the 
outflow  of  water  on  frozen  lakes. If 

VOLCANIC  ACTIVITY  ATTRIBUTED  TO  :  ** 

1.  Presence  of  water  (they  follow  oceans). tt 

2.  Contraction  of  the  earth's  crust  where  strains  cannot  be  resisted,  and 

the  relief  of  downward  pressure. 

3.  Permanent  lines  of  weakness  of  earth's  crust. 

The  volcanic  lines  are  approximately  the  same  as  formerly,  as  if  these 

lines  were  fixed. 
Why  this  is  possibly  true. 

*  Fouqu6.    Santorin  et  ses  eruptions,  XVI. 

t  A  bibliography  of  Graham's  Island  is  given  in  Johnston-Lavis'  "  South  Italian  vol- 
canoes," 105-107. 

1 1.  C.  Russell's  Volcanoes  of  North  America.  276-281.  —  Kotzebue's  Voyage  of  discovery. 
II,  180-181.  1821. 

Volcanic  eruptions  in  the  Bering  Sea.  By  Geo.  Davidson.  Bui.  Am.  Geog.  Soc.,  1890, 
XXII,  267-272. 

I  Barrows.  Nat.  Geog.  Mag.,  Sept.  1900,  XT,  348-350.  —  Scottish  Geog.  Mag  ,  May  1901, 
XVII,  263-264. 

I  The  Malay  Archipelago.    9.    London,  1894. 

II  Ice  ramparts.    By  E.  R.  Buckley.    Trans.  Wis.  Acad.  Sci.,  XIII,  156-157. 

**  Les  volcans  et  les  causes  qui  paraissent  les  determiner.  Par  Virlet  d'  Aoust.  Con- 
eres  International  de  Geologic,  1878,  pp.  239-248. 

tt  J.  W.  Judd.  The  eruption  of  Krakatoa.  Rep.  Krakatoa  Com.  of  the  Roy.  Soc.,  46.  Lon- 
don, 1888. 


151 


152  DORMANT   VOLCANOES. 


II.  DORMANT  OR  EXTINCT  VOLCANOES. 

1.  Some  volcanoes  always  active. 

2.  Some  are  quiet  for  years. 

Mont  Pel6e,  Martinique,  had  no  eruptions  from  1851  to  1902. 

3.  Some  are  quiet  for  centuries. 

Once  extinct,  a  volcano  crumbles  rapidly. 
If  the  climatic  conditions  are  favorable,  volcanic  rocks  usually  make  good 

soils. 
Examples  of  extinct  volcanoes. 

Crater  lake,*  southwest  Oregon  ;  surface,  6,239  feet  a.  t.  ;  5-6  miles  in 
diameter;  no  outlet;  maximum  depth  of  water,  2,000  feet  ;  walls 
above  water,  500  to  2,200  feet;  total  depth  of  crater,  2,900  to 
4,200  feet. 

Theories  of  its  origin. 

The  San  Francisco  mountains  near  Flagstaff,  Ariz.     Many  cones  to  be 
seen  from  the  Santa  Fe  and  Southern  Pacific  railways  through 
the  Colorado  desert. 
Marysville  buttes,  California,  t 
The  latest  eruptions  on  the  Pacific  coast  of  the  United  States  have 

taken  place  within  historic  times.  t 
The  cones  of  central  Fr-ance§  and  Germany.  || 
Ancient  lavas. 

Cascade  range  volcanic. 

In  the  Sierras  on  top  of  auriferous  gravels;  capping  many  mountains 

in  Arizona. 

Sheet  near  Stanford  University  ;  Frenchman's  Lake,  basaltic  columns. 
The  Palisades  of  the  Hudson  is  the  edge  of  a  lava  sheet. 
Giant's  Causeway,  Ireland  ;  sheet  covers  2,000  square  miles. 
Great  sheet  from  northwest  Wyoming  down  Snake  river,  2,000  to  over 
4,000  feet  thick,  and  covering  an  area  of  more  than  180,000  square 
miles. 
In  India  the  Deccan  lava  sheet  covers  an  area  of  200,000  square  miles 

to  a  depth  of  2,000  to  6,000  feet.  IF 
Dikes. 

Lavas  cooled  in  crevices.** 

Effect  of  temperature  of  rocks  on  size  of  dikes. 

Stand  out  as  walls  ;tt  Spanish  Peaks  of  Colorado.  U 

*  Science,  1886,  VIII,  179-182.  —  8th  ann.  rep.  U.  S.  Geol.  Surv.,  157-158.  Washington,  1889. 

Crater  Lake  special  map.    By  J.  S.  Diller.    U.  S.  Geol.  Surv.,  n.  d. 

t  Marysville  folio,  U.  S.  Geol.  Surv.    By  W.  Lindgren  and  H.  W.  Turner. 

J  J.  S.  Diller.    Science,  May  5,  1899,  p.  639. 

?  Scrope's  Volcanos  of  France.    57-67.    London,  1862. 

8  Major-General  Nelson.    Jour.  Roy.  Geol.  Soc.  of  Ireland,  II,  107-109.    Edinburg,  1871. 


t  Geology  of  India.    Am.  Jour.  Sci.,  XIX,  140,  p.  300.    New  Haven,  1880. 
**  Open-air  studies.    By  G.  A.  J.  Cole.    Plate  VII,  opp.  181.     London,  1895. 
tt  Across  Vatna  Jokul.    By  W.  L.  Watts.     101,109,119,153-157.     London,  1876. 


On  veins  and  dikes,  see  Crosby  in  Tech.  Quar.,  Dec.  1896,  IX,  355. 
U  Spanish  Peaks  folio,  U.  S.  Geol.  Surv.,  71.    By  R.  C.  Hills. 


153 


154 


Fig.  34.— Trap  dikes  cutting  granite,  Bear  Island  (100  feet  high),  Labrador.    (Daly.) 

Laccolites.* 

Lavas  intruded  between  beds. 
Tuffs. 

Fragmental  ejectamenta,  often  covering  large  areas. 


Fig.  35. — West  Spanish  Peak,  Colorado,  from  the  northwest,  with  vertical  dikes. 
(Hills.) 


*  Geology  of  the  Henry  Mountains.    By  G.  K.  Gilbert.  —  Laccolites  in  Colorado.    By  G. 

K.  Gilbert.    Jour.  Geol.,  IV,  816.    Chicago,  1895. 
The  laccolitic  mountain  groups  of  Colorado,  Utah,  and  Arizona.  By  W.  Cross.   14th  ann. 

rep.  U.  S.  Geol.  Surv  ,  157-341.    Washington,  1895. 


155 


156 


IGNEOUS    ROCKS. 


Fig.  36.— The  great  north  dike  of  West  Spanish  Peak,  Colorado.     At  this  point  it  forms 
a  wall  100  feet  in  height.    (Hills.) 

AGES  OF  VOLCANOES. 

Why  the  rocks  contain  no  fossils  except  in  cases  of  tuffs  and  inclusions. 
Age  shown  by  relations  to  adjacent  rocks. 


ECONOMICS  OF  IGNEOUS  ROCKS. 
Fertility  of  soils.* 

Vesuvius  and  Etna  covered  with  vines  and  towns. 

Volcanic  cinders  quickly  make  excellent  soils  when  the  fall  is  not  more 
than  six  or  seven  inches  thick. 

Java  and  Japan  thickly  populated. 
Sulphur  deposits  of  Sicily,  Italy,  and  Iceland. 
Ores  often  concentrated  next  to  dikes  and  in  eruptives. 
Use  of  basalt  for  road  material  at  Stanford. 
Tuffs  and  fragmental  andesites  do  not  hold  water. 

Examples:  Frenchman's  Lake;  Sierra  ditches. 
Used  for  railway  ballast  in  Arizona. 
Pozzuolana  used  in  making  hydraulic  cement. 

*  Lavas  and  soils  of  the  Hawaiian  Islands.    By  W.  Maxwell,  etc.     Exp.  Sta.  Rec.  U.  S. 
Dept.  Agr.,  X,  no.  6,  pp.  525-531.     Washington,  1899. 


157 


158 


Geysers.* 

Geyser,  a  gusher.     Forbes  says  it  means  "a  rager";  it  is  applied  to  any 

noisy  water  in  Iceland.     (Forbes,  Iceland,  230.) 

"  Geysir  is  a  common  name  for  all  fountains,  and  is  derived  from  the 
Icelandic  word  geysa,  to  ascend  violently,  though  it  is  now  al- 
most exclusively  applied  to  the  great  gey  sir."  t 
Geysers  are  periodically  eruptive  hot  springs. 
Always  hot. 
Distribution. 
Iceland. 

U.  S.  Colombia,  near  Cartagena  on  Rio  Magdalena.i 
New  Zealand. § 
Yellowstone  National  Park. 
All  in  regions  of  former,  or  recent,  volcanic  activities. 

Phenomena  of  eruption  of  the  great  geysers  of  Iceland  remarkably  like 
volcanic  eruptions. 

1.  Cannonading — steam  bubbles  collapsing  like  singing  of  kettles. 

2.  Bulging  of  water  and  overflow. 

3.  Leaping  upward  of  water,  about  100  feet. 

4.  Escape  of  steam  with  noise. 
Frequency  diminishing .  || 

In  1804  the  geysers  of  Iceland  erupted  every  hour;  now  the  interval  is 

of  a  few  days. 

Dying  out  less  marked  in  the  Yellowstone  region. 
In  Yellowstone  National  Park  there  are  more  than  3,000  vents. 
Basin  three  miles  wide,  honey-combed. 

Grand  geyser  temp.  150°,  throws  water  200  feet  and  steam  1,000  feet. 
Giantess  throws  a  column  20  feet  in  diameter  and  60  feet  high. 
Smaller  pits  throw  water  250  feet  high. 
Some  erupt  for  hours. 

*  Bibliography  of  geysers  in  Peale's  12th  aim.  rep.  U.  S.  Geol.  Surv.  of  the  Territories. 

1878,  pt.  II,  427-149.    Washington,  1883.  —  Geysers.    By  W.  H.  Weed.    School  of 

Mines  yuar.,  July  1890,  XI,  289-306. 

Yellowstone  National  Park  folio,  U.  S.  Geol.  Surv.,  no.  30.    Washington,  1896. 
t  A  summer  in  Iceland.    By  C.  W.  Paijkull.    320.     London,  1868. 
t  Vues  des  Cordilleres,  etc.    Par  A.  de  Humboldt.    239,  241,  and  plate  opp.  p  239.    Paris, 

II  The  rapid  decline  of  geyser  activity  in  Yellowstone  Park.    By  E.  H.  Harbour.    Jour. 

Franklin  Inst.,  Mar.  1900,  CXLIX,  236.—  Abstract.    Proc.  A.  A.  A.  Sci,  vol.  48,  p.  230. 
'i  A  visit  to  the  New  Zealand  volcanic  zone.    By  H.  M.  Cadell.    Trans.  Edin.  Geol.  Soc., 

1897,  VII,  183-200. 


159 


160 


GEYSERS. 


THEORIKS  OF  THE  CAUSES  OF  ERUPTIONS. 

Mackenzie's  theory.* 
Bunsen's  theory. t 

Downward  removal  of  boiling-point. 

The  greater  the  pressure,  the  higher  the  temperature  required. 

Artificial  geysers. 

Relations  of  the  overflow  to  eruptions.! 


Fig.  37. — Mackenzie's  diagram  illustrating  his  theory  of  the  cause  of  geyser  periodicity. 

CONDITIONS  NECESSARY  TO  GEYSERS. 

1.  Igneous  acid  rocks,  hot  above  the  boiling-point  beneath  the  surface,  and 

cooler  at  and  near  the  surface. 

2.  Meteoric  waters  having  access  to  hot  rocks,  or  to  vapors  ascending  from 

hot  rocks. 

3.  Tube  for  escape  of  water  and  steam. 

*  Travels  in  the  island  of  Iceland.    By  Sir  George  Steuart  Mackenzie.    2d  ed.,  226-229. 

London,  1812. 

t  Heat  as  a  mode  of  motion.    By  J.  Tyndall.    168.    New  York,  1888. 
j  Some  conditions  affecting  geyser  eruption.    By  T.  A.  Jaggar,  Jr.    Am.  Jour.  Sci.,  May 

1898,  V,  323^333. 


161 


162  KARTHQUAKKS. 

Effect  of  soaping  geysers. 

Resemblance  of  geyser  eruptions  to  "  bumping." 

Bumping  more  marked  in  dense  liquids. 

Soaping  increases  the  viscosity  of  the  water.* 
Geologic  work  of  geysers. 

AVhy  cones  are  built  around  vents. 

Relief  of  pressure  and  cooling. 

Fire-hole  fork  of  Madison  river  deposits  silica. 

Petrifying  of  trees,  twigs  coated. 

Gardiner's  river  deposits  travertine  in  terraces. t 


Hot  Springs. 

The  high  temperature  of  hot  springs  caused  by  surface  waters  coming  in 

contact  with  hot  rocks  before  the  waters  emerge. 
When  the  conditions  of  supply  and  emergence  are  favorable,  geysers  are 

formed,  but  otherwise  only  hot  springs. 
In  most  cases  hot  springs  never  have  been  geysers,  and  there  is  little  or  no 

evidence  of  hot  rocks  about  them. 
Terraces  formed  by  hot  springs. 
Method  of  formation. 
Possibility  of  heat  being  caused  by  — 

1.  Chemical  reaction. 

2.  Burning  coal. 

Hot  springs  vary  little  in  flow;  they  are  deep-seated. 
Supposed  medicinal  properties  of  hot  springs.; 


Earthquakes.^ 

Earthquakes  are  vibrations,  or  jars,  rock-  or  earth-waves,  propagated  through 

the  earth's  crust.    These  are  produced  by  concussions  in  the  crust. 
The  science  of  earthquakes  called  Seismology. 

*  Experiments  with  an  artificial  geyser.  By  J.  C.  Graham.  Am.  Jour  Sci.,  Jan.  1893, 
CXLV.  54. —  Soaping  geysers.  By  Arnold  Hague.  Trans.  Am.  Inst.  Min.  Eng., 

t  Some  geological  causes  of  the  scenery  of  Yellowstone  National  Park.  By  A.  R. 
Crook.  Am.  Geol.,  Sept.  1897,  XX,  159-167. 

A  visit  to  the  New  Zealand  volcanic  zone.  By  H.  M.  Cadell.  Trans.  Edin.  Geol.  Soc., 
VII,  192.  Edinburg,  1897. 

t  The  mineral  waters  of  Arkansas.    By  J.  C.  Branner.    10.    Little  Rock,  1892. 

2  Les  tremblements  de  terre.    Par  F.  Fouque.    Paris,  1889. 

Great  Neapolitan  earthquake  of  1857.  The  first  principles  of  observational  seismology. 
By  Robert  Mallet.  2  vols.  London,  186-2. 

Transactions  of  the  Seismological  Society  of  Japan.  Vols.  I  to  XVI,  1880  to  1892.  —  Seis- 
mology in  Japan.  By  J.  Milne.  Nature,  April  18,  1901,  pp.  588-589. 

The  Charleston  earthquake  of  August  31,  1886.  By  C.  E.  Dutton.  9th  ann.  rep.  U.  S.  Geol. 
Surv.,  203-528.  Washington,  1889. 

La  face  de  la  terre.    Par  E.  Suess.    Tome  I,  96-137.    Paris,  1897. 

John  Milne,  observer  of  earthquakes.  By  Cleveland  Moffett.  McClure's  Mag.,  May 
1898,  pp.  17-27. 

Seismology.    By  John  Milne.    Internal.  Sci.  Series.     London,  1898. 

Methods  of  studying  earthquakes.  By  Charles  Davison.  Jour.  Geol.,  VIII,  301-308.  Chi- 
cago, 1900. 


163 


164  EARTHQUAKES. 

Concussions  may  be  caused  by  — 

1.  Snapping  of  rocks  under  strain. 

Exemplified  by  the  suddenness  with  which  ice  breaks  in  lakes.* 

2.  Slipping  of  rocks  on  each  other.     Readjustment. 

3.  In  vicinity  of  volcanoes,  by  explosions  within,  possibly  the  forming 

and  collapsing  of  steam. 

To  understand  earthquakes  it  is  necessary  to  study  propagation  of  waves 
through  rocks  under  complex  conditions  of  various  structures,  com- 
positions, and  strains. 
Wherever  faults  are  common  in  the  rocks  earthquakes  must  have  occurred, 

even  though  they  may  now  be  extremely  rare.t 
Every  readjustment  must  cause  jars. 

Note  folded  and  faulted  Appalachians;  faults   10,000+  feet ;  Scotland; 

Alps ;  faults  of  California. 

Irregularity  of  sea  bottom  and  possible  slips  there. 
Hence,  jars  are  to  be  expected  along  lines  of  weakness  and  readjust- 
ment.    Volcanic  regions  are  regions  of  readjustment. 
But  the  wave  travels  at  different  rates,  owing  to  the  difference  in  the  con- 
ductivity of  rocks. 
In  loose  sand,  984  feet   per   second;   sandstone,  7,400   feet  per 

second;  granite,  9,200  feet  per  second.} 
Explosions  at  Hell  Gate,  New  York,  observed  in  Boston,  Mass.,  gave  a 

rate  of  transmission  of  4,500  to  20,000  feet  per  second. 
The  form  of  the  wave  at  the  surface  is  determined  by  these  differences 

in  conductivity. 
Epicentrum. 

Location  of  epicentrum. 
Coseismal  lines. 

The  form  of  coseismal  lines  found  by  time  observations. 
Focus. 

Depth  of  focus. 

Charleston  earthquake  12  miles.$ 
Some  foci  are  about  4  miles  below  the  surface. 
Displacement. 

The  amount  of  displacement  of  an  earth  particle  is  seldom  more  than 
3  or  4  millimeters;  sometimes  it  is  only  a  fraction  of  a  milli- 
meter. 
The  maximum  displacements  observed  at  the  Lick  Observatory  have 

been  — 

June  20,  1897,  0.20  inch. 

March  30,  1898,  0  22  inch. 

The  average  is  about  0.03  inch. 

*  Ice  ramparts.    By  E.  R.  Buckley.    Trans.  Wis.  Acad.  Sci.,  XIII,  160. 

t  The  Hereford  earthquake  of  December  17,  1896.    By  Charles  Davison.    Birmingham, 

1899.  Nature,  June  29,  1899,  pp.  194-195. 

t  On  the  velocity  of  seismic  waves  in  the  ocean.    By  Charles  Davison.    Phil.  Mag..  Dec. 

1900,  p.  579.  —  Am.  Jour.  Sci.,  Jan.  1901,  p.  95. 

Propagation  of  earthquake  waves  through  the  earth.     By  C.  G.  Knott.     Proc.  Roy.  Soc. 

Edinburg,  XXII,  573-585. 
§  Dutton.    9th  ann.  rep.  U.  S.  Geol.  Surv.,  311.    Washington,  1889. 


165 


166  EARTHQUAKES. 

A  displacement  of  0.01  inch  is  readily  perceptible.    (Director  Campbell.) 
One  was  reported  in  Japan  in  1891  as  "  not  less  than  one  foot."  * 
(This  does  not  refer  to  vibrations  of  swinging  objects,  or  to  the  dis- 
placement where  a  crack  or  fault  is  produced.) 
Form  of  movement. 

Shown  by  seismograph. t 

Comments  on  the  direction  of  the  movement. 
Influence  of  position  in  relation  to  focus. 

At  Riobama  in  1797  bodies  were  thrown  several  hundred  feet  in  the  air. 
Reflex  action. 

Effect  in  mines  and  at  surface. 
Sometimes  not  felt  as  strongly  in  mines  as  on  top. 
Cause  of  variation. 
Frequency.^ 

The  frequency  varies  with  locality ;  there  are  two  a  day  in  Japan. 

Common  in  volcanic  regions. 

California  is  a  region  of  faults  and  extinct  volcanoes. 

Has  the  weather  any  influence  upon  earthquakes?  $ 

18279  records  in  Japan  show  that  earthquakes  originating  on  land 
in  that  country  are  affected  by  barometric  pressure;    yet 
pressure  may  be  high  without  producing  them.jl 
Limits  of  area. 

Sometimes  shocks  are  felt  over  areas  of  thousands  of  square  miles,  even 
over  the  whole  world. If     In  California  they  are  often  felt  over  a 
few  miles  only. 
Sounds  produced  by  earthquakes.** 

RESULTS  OF  EARTHQUAKES.-!-)- 
Fissures  and  faults. 

Japanese  earthquakes  and  faults. it 

Sonora,  Mexico,  shock  in  1887 ;  crack  100  miles,  fault  8  feet.§§ 

Arizona.  ||  || 

New  Zealand,  1848;  60  miles  long,  18  inches  throw. 

New  Madrid,  Missouri,  chasm  opened. 

Inyo,  California,  shock  of  1872;  crack  40  miles  long,  fault  25  feet.  If  IT 

*  Geol.  Mag.,  Sept.  1898,  p.  429. 

t  See  records  in  the  Journal  of  Seismology. 

1  The  periodicity  of  earthquakes.    By  R.  D.  Oldham.    Geol.  Mag.,  Oct.  1901,  VIII,  449. 

\  Personal  narrative  of  travels.    By  A.  de  Humboldt.    II,  215-220.    London,  1822. 

|  Milne.    Nature,  June  26,  1902,  p.  202. 

\  Observations  of  earthquakes.    By  H.  F.  Reid.    Johns  Hopkins  University,  circular  no. 

152,  p.  3,  May  1901. 
The  propagation  of  earthquake  motions  to  great  distances.  By  R.  D.  Oldham.  Am.  Jour. 

Sci.,  April  1900,  CLIX,  306-307.— Proc.  Roy.  Soc.,  LXVI,  2. 
Nature,  Oct.  13,  1898,  p.  586. 

**  Earthquake  sounds.  By  C.  Davison.  Am.  Jour.  Sci.,  Apr.  1900,  p.  307. 
ft  Some  remarkable  earthquake  effects.  Nature,  Nov.  22,  1900,  pp.  87-88. 
+t  On  the  cause  of  the  great  earthquake  in  central  Japan,  1891.  By  B.  Koto.  Jour.  Coll. 

Sci.,  Imperial  University  of  Japan,  V,  pt.  IV,  plates.    Tokyo,  1893. 
??  Science,  Aug.  12,  1887,  X,  81. 
HI  Kemp's  Ore  deposits.     15.    New  York,  1893. 
VS  Nature,  Nov.  8,  1883,  XXIX,  45. 


167 


168 


EARTHQUAKES. 


The  deluge  of  the  Bible 
lower  Euphrates  by 
an  earthquake.* 
Joints  in  rocks. 

Rocks  bend  slowly, 
but  snap  when 
under  strain, 
or  from  a  sud- 
den jar. 

Earthquake  waves  (im- 
properly called  tid- 
al waves)  may  be 
due  to  sudden  lift- 
ing or  lowering  of 
the  water  surface. 
Destruction  wrought 

by  wave. 
Examples  :     Ja- 
pan, t  Lisbon. 
Landslides,     if     in     wet 
weather. 


supposed  to  be  due  to  the  inundation  of  the 


Fig.  38.—  Fault  having  both  vertical  and  horizontal  dis- 
, formed  during  an  e 
in  Japan.     (Koto  ) 


. 

placement,  formed  during  an  earthquake 
(Ko 


Fig.  39.— Fissure  and  fault  in  Arizona  produced  at  the  time  of  an  earthquake. 

*  La  face  de  la  terre..  Par  E.  Suess.    Tome  I,  25-95.    Paris,  1897 

t  Across  America  and  Asia.    By  R.  Pumpelly.     107.    London,  1870.  —  Nat.  Geog.  Mag. 
Sept.  1896,  VII,  285-289,  310. 


169 


170  CHANGES    OF    LEVEL. 

Lakes  and  pools  formed. 

Slides  dam  streams;  breaking  of  such  dams  is  dangerous. 

Case  in  India  in  1897. 
Drying  up  of  springs. 

Water  turned  into  other  channels. 

Terrors  of  earthquakes  due  to  the  fact  that  there  is  no  means  of  predicting 
the  time  or  nature  of  the  shock,  and  to  the  instability  of  the  earth, 
which  is  the  very  type  of  stability. 
No  courage  or  skill  can  prevent  them. 

From  the  faulted  and  slicken-sided  condition  of  the  rocks  it  is  inferred 
that  California  always  has  been  and  probably  always  will  be  a 
region  of  earthquakes. 

PRECAUTIONARY  MEASURES. 

Destruction  of  life  mostly  caused  by  the  falling  of  walls  of  houses. 
Catania,  Sicily,  earthquake  in  1693;  100,000  killed.* 
Lisbon  earthquake,  1755,  killed  60,000,  but  largely  by  wave  on  wharves. 
Japan  earthquake  of  1896  killed  26,975,  mostly  by  wave  dashing  upon 

the  shores. 

Riobamba,  Equador.     (See  Whymper.) 

The  city  of  Mendoza,  Argentine  Republic,  entirely  destroyed  in  1861. t 
Japanese  houses  built  of  wood. 
Earthquake  houses  placed  on  balls. 
Destruction  in  California  really  very  small. 


Changes  of  Level.* 
Is  it  possible  that  the  sea-level  itself  may  change?  § 

Changes  of  level,  either  elevation  or  depression,  sometimes  accompany 

earthquakes  and  volcanic  eruptions. 
Sometimes  abrupt,  as  at  St.  Thomas,  W.  I. 
Sometimes  quiet,  slow,  and  uniform. 

In  any  case  they  are  due  in  part,  at  least,  to  agencies  connected  with 
the  interior  condition  of  the  earth. 

EVIDENCES  OF  ELEVATION. 

1.  Dead  marine  organisms,  or  their  skeletons,  on  dry  land. 

2.  Work  of  marine  animals  on  land. 

3.  Work  of  waves  (either  constructive  or  destructive)  on  shore  lines  now 

out  of  the  reach  of  waves. 

4.  Human  records. 

5.  Eroded  surface  of  marine  sediments. 

*  Sir  W.  Hamilton's  Observations.    59.    London,  1774. 

t  The  highest  Andes.    By  E.  A.  Fitzgerald.    19-20.    New  York,  1899. 

t  Untersuchungen  iiber  das  Aufsteigen  und  Sinken  der  Kusten.    Von  Friederich  Gustav 

Hahn.    Leipzig,  1879. 

Travels  in  Peru.    By  J.  J.  Von  Tschudi.    41-46.    London,  1847. 
I  Oscillations  in  the  sea-level.    By  H.  W.  Pearson.    Geol.  Mag.,  April  1901,  VIII,  167-174; 

May  1901,  VIII,  223-231;  June  1901,  VIII,  253-264. 


171 


172 


EVIDENCES    OF    ELEVATION. 


I.  Dead  marine  organisms,  or  skeletons,  on  land. 

Coral  reefs  of  St.  Thomas,  W.  I. 

Raised  reefs  of  Mombasa,  East  Africa.* 

Raised  reefs  of  Cuba,  1,000  to  1,100  feet  a.  t. 

Raised  reefs  of  Peru,  3,000  feet  a.  t.  ;t  of  Lau  Islands,  Fiji,  1,000  feeU 

Fossils  (oysters,  barnacles,  and  sea-urchins)  on  the  basaltic  columns 

near  Stanford  University. 
Shells  of  Baffin  Land.§     Elevation  270  to  300  feet. 

II.  Work  of  marine  animals  on  land. 

Sea-urchin  holes  about  the  bay  of  Rio  de  Janeiro,  3  feet  a.  t.,  and  on 

the  coast  of  Pernambuco.     (See  Plate  XII.) 
Pholas  holes  with  shells  at  Purissima. 
Pholas  and  worm-tubes  on  the  Page  Mill  road. 
Lithodomus  of  the  temple  of  Jupiter  Serapis,  Italy. || 

III.  Wave  work  (either  constructive  or  destructive)  now  beyond  the  reach  of 

waves . 
Terraces  and  old  beaches  at  Santa  Cruz. 


Fig.  40. — A  line  of  erosion  about  the  base  of  a  granite  peak  at  Victoria,  Brazil.    The 
notch  is  now  about  two  meters  above  tide-level. 


*  Gregory's  Great  drift  valley.    45.  51,  55.    London,  1896. 

t  A.  Agassiz.    Proc.  Am.  Acad.  Sci..  XI,  287.    1876. 

t  A.  Agassiz.    Am.  Jour.  Sci.,  April  1902,  p.  308. 

g  Elevations  of  Baffin  Land.    By  T.  L    Watson.    Jour.  Geol.,  1897,  V,  17-33.  -  Partial 

bibliography  for  North  America,  32-33. 
I  Le  temple  de  S6rapis  a  Pouzzoles.    Chap,  ix  of  La  face  de  la  terre.    Par  E.  Suess.    II, 


173 


174  EVIDENCES    OF    DEPRESSION. 

San  Pedro  hill,  near  Los  Angeles,  terraced. 

Santa  Catalina  islands. 

Drift  timber  on  Hudson  bay  above  tide.* 

Conflicting  evidenced 
Terraced  fjords  of  Norway.* 
Raised  beaches  of  Baffin  Land.§ 

IV.  Human  records. 

Precise  levels  disclose  relative  land  movements. 

Scandinavia  rising  north  of  Stockholm  at  the  maximum  rate  of  5-6 
feet  per  century,  or  0.72  of  an  inch  in  a  year. 

V.  An  eroded  surface  of  marine  sediments.     (Unconformity  is  explained  at 

length  in  Part  II.) 

AMOUNT  OF  ELEVATION. 

The  amount  of  elevation  is  sometimes  shown  approximately  by  the  heights 
of  marine  sedimentary  rocks  above  the  sea. 

EVIDENCES  OF  DEPRESSION. 

Evidences  of  depression  are  more  difficult  to  see,  because  the  land  surface 
goes  beneath  the  water.     Often  it  is  re-elevated  and  uncovered. 

I.  Land  plants  in  place  covered  by  marine  deposits,  or  below  sea-level. 

Stalactites,  lignite,  and  erect  stumps  found  45  feet  below  sea-level  in 

Bermuda.  || 

Peat  below  tide  on  the  bay  of  Fundy.H 
Stumps  beneath  marine  deposits  in  Louisiana. 
In  New  Jersey  cedar  stumps  on  beach  reached  by  salt  water.** 
Trees  in  Muir  inlet  exposed  at  low  tide.ft 
Coal  beneath  the  sea  in  Peru. 
Coal  in  Pennsylvania  overlain  by  marine  fossils. 

II.  Corals  faund  (in  wells)  below  depth  at  which  they  live  (150  feet). 
Recent  boring  (Oct.  1897)  in  northeast  Australia,  698  feet  in  coral.it 

III.  Submerged  valleys,  or  river  channels.^ 
Valleys  can  be  cut  in  certain  forms  only  on  land. 

*  Robert  Bell.    Am.  Jour.  Sci.,  Mar.  1896,  CLI,  219-228. 

t  Stability  of  the  land  around  Hudson  Bay.  By  J.  B.  Tyrrell.  Geol.  Mag.,  June  1909,  p. 
266. 

t  Raised  shore  lines  at  Trondhjem.    By  W.  Upham.    Am.  Geol.,  Sept.  1898,  XXII,  149-154. 

Etud  sur  le  soulevement  lent  actual  de  la  Scandenavie.  Par  A.  Badoureau.  Ann.  des 
Mines,  9me  ser.,  VI,  239-275.  Paris,  1894. 

The  glacial  period  and  oscillations  of  land  in  Scandinavia.  By  N.  O.  Hoist.  Geol.  Mag., 
VIII,  205-216.  London,  1901. 

g  Evidences  of  recent  elevation  of  the  southern  coast  of  Baffin  Land.  By  Thos.  L.  Wat- 
son. Jour.  Geol.,  1897,  V,  17-33. 

I  Notes  on  the  geology  of  Bermuda.    By  A.  E.  Verrill.    Am.  Jour.  Sci.,  May  1900,  CLIX, 

325. 
Recent  observations  in  the  Bermudas.    By  J.  M.  Jones.    Nature,  VI,  262. 

II  Canadian  Naturalist,  2d  ser.,  1881,  IX,  373. 

**  Ann.  rep.  State  Geol.  New  Jersey,  1885,  p.  93. 
-(•  Reid.    16th  ann.  rep.  U.  S.  Geol.  Surv.,  I,  440.    Washington,  1896. 
It  Nature,  Mar.  24,  1898,  LII,  494-495;  July  7,  1898,  LIII,  221. 

?g  T.  Codrington.  Submerged  rock  valleys  in  South  Wales,  Devon,  and  Cornwall.  Quar. 
Jour.  Geol.  Soc.,  Aug.  1898,  LIV,  251-278. 


175 


176  EVIDENCES   OF    DEPRESSION. 

Firths  of  Scotland.     England.* 

Fjords  of  Norway  ;t  coast  of  Maine.* 

Filled-up  bays  of  Ocean  side,  California;  of  New  Jersey. 

Drowned  valleys  of  the  west  coast  of  the  United  States.^ 

Drowned  valley  at  New  York.|| 

IV.  Distribution  of  plants  and  animals. 

Identity  of  Santa  Catalina  island  plants  with  those  of  the  mainland. 
Elephants'  teeth  found  on  Santa  Rosa  island  and  on  mainland. 
Elephants  on  St.  Paul  island  show  sinking  to  disconnect  it  from  main- 
land. 

Great  Britain's  former  connection  with  Europe. f 
Wallace's  work  on  Malay  archipelago. 

Professor  C.  H.  Gilbert's  work  on  the  distribution  of  Pacific  coast  fishes. 
Case  of  the  Isthmus  of  Panama.** 
Resemblance  of  the  faunas  of  South  America  and  New  Zealand. 

V.  Historical  records. 

In  Scania,  south  Sweden,  some  of  the  streets  are  below  water. 

Dunkirk  fields. ft 

Tilting  of  the  region  of  the  Great  Lakes. 

Observations,  from  20  to  37  years,  show  changes  from  0.061  to  0.239 

feet.iJ 

Spanish  building  at  the  mouth  of  the  Mississippi  river.§§ 
Leveling  in  France  shows  the  southeastern  part  of  that  country  to  be 
fixed,  while  the  northwest  and  northeast  have  sunk  between  the 
years  1863  and  1899. |||| 

VI.  Great  thickness  of  sediments. 

Sediments  of  great  thickness  could  accumulate  only  during  a  long  and 

gradual  depression. 

Example:  Arkansas  Valley  trough,  where  the  coal  measures  (sedi- 
ments) are  23,780  feet  thick. if  IF 

*  Submerged  terraces  and  river  valleys  bordering  the  British  Isles.    By  E.  Hull.    Geol. 

Mag.,  Aug.  1S>8,  pp.  351-357.  —  Jukes-Brown.    Geol.  Mag..  Sept,  1898,  p.  429. 
t  Fjords  and  submerged  valleys  of  Europe.    B.  W.  Upham.    Am.  Geol.,  Aug.  1898,  XXII, 

101-108. 
Topographish-geologische  Studien  in    Fjordgebieten.    Von    Otto    Nordenskiold.    Bui. 

Geol.  Inst.  Univ.  Upsala,  IV,  157-228.    Upsala,  1900. 
Science,  June  28,  1901,  p   1034. 
Die  Fjordbildungen.    Ein  Beitrag  zur  Morphologie  der  Kiisten.    Iiiaug.  Diss.  von  Paul 

Dinseaus.    Berlin,  1894. 
t  Henry  Gannett.    Physiographic  types.    Folio  1,  Physiography.    Topographic  Atlas 

U.  S.    Washington,  1898. 
?,  The  submerged  valleys  of  the  coast  of  California,  etc.    By  George  Davidson.    Proc. 

Cal.  Acad.  Sci.,  3d  ser.,  I,  73-101.    San  Francisco,  1897. 
W.  E.  Ritter.    Science,  Oct.  11,  1901,  XIV,  575. 
A  topographic  study  of  the  islands  of  Southern  California.     By  W.  S.  T.  Smith.    Bui. 

Dept.  Geol.,  Univ.  California,  II.  179-230     Sept.  1900 

LLindenkohl.    Am.  Jour.  Sci  ,  1885,  CXXIX,  475-480. 
Wallace's  Malay  Archipelago.    8,  10-14.     London  and  New  York,  1894. 
The  geological  history  of  the  Isthmus  of  Panama.    By  R.  T.  Hill.    Bui.  Mus.  Comp. 

Zool.,  1898,  XXVIII,  266-270. 
tt  L'atlaisement  du  sol  des  Pays-bas.    Par  Jules  Girard.    Bui.  Soc.  Geog.,  Oct.  1879,  pp. 

U  Modification  of  the  Great  Lakes  by  earth  movement.    By  G.  K.  Gilbert.    Nat.  Geog. 

Mag.,  Sept.  1897.  VIII,  233-247. 
??  Nat.  Geog.  Mag.,  VIII,  352. 
Hi  Le  nivellement  general  de  la  France.    Par  Charles  Lallemand.    Ann.  des  mines, 

9me  se>.,  XVI,  227-306.    Paris,  1899. 
Affaisement  du  sol  de  la  France.     Par  E.  Van  den  Broeck.      Bui.  Soc.  Beige  de  G&>1.,  V, 

13-20.    Bruxelles,  1891. 
«iH  Thickness  of  the  Paleozoic  sediments  in  Arkansas.      By  J.  C.  Branner.     Am.  Jour. 

Sci.,  Sept.  1896,  pp.  229-236. 


177 


178  RATE   OF   CHANGES. 

VII.  Faults  with  large  vertical  displacements. 

A  fault  in  the  coal  fields  of  Alabama  has  a  throw  of  10,000  feet  or  more, 
and  the  downthrow  side,  with  coal  beds,  is  carried  far  below 
ocean-level.* 

VIII.  Wide  distribution  of  heavy  conglomerates. 

Heavy  water-worn  boulders  could  be  formed  over  a  wide  area  only  by 
the  place  passing  through  a  beach  condition,  and  this  would  re- 
quire a  gradual  depression  of  the  land.t 
Distribution  of  changes. 

No  part  of  the  earth's  crust  is  quiet. 

Behavior  of  delicately  adjusted  seismoscopes. 
Some  parts  change  more  rapidly  than  others. 

RATE  OF  CHANGES. 

The  rate  must  necessarily  vary  greatly.     Darwin  mentions  flat  island  of 
Santa  Maria  raised  at  a  jump,  and  he  found  on  land  "  gaping,  putre- 
fying mussel-shells,  still  attached  to  the  bed  on  which  they  had 
lived,  "t 
St.  Thomas  raised  at  a  jump,  bringing  up  live  corals  to  perish  on  the 

beach . 

Gilbert  cites  tilting  about  the  Great  Lakes  at  the  rate  of  0.42  feet  a 
century  in  100  miles. §    The  Niagara  river  will  cease  to  flow  in 
3,000  years,  if  the  present  rate  of  tilting  continues. 
Norway,  north  of  Stockholm,  rising  5  to  6  feet  per  century. 
New  Jersey  coast,  from  Long  Island  to  Cape  May,  is  sinking  at  the  rate 
of  2  feet  per  century. 

CAUSES  or  ELEVATION  AND  DEPRESSION. 
Theories. 

1.  Internal  heating  and  cooling  of  the  rocks. 

2.  Denudation  and  deposition. 

Theory  of  isostacy.|| 

3.  Change  of  physical  condition  of  the  interior. 

Contraction  of  rocks  on  changing  to  crystalline  condition. 

4.  Loss  of  water,  air,  and  gases. 

5.  Thrusts  or  stresses,  however  produced,  that  cause  bending  or  fault- 

ing of  the  beds. 

*  Branner.    Am.  Jour.  Sci.,  Nov.  1897,  IV.,  364-365. 

t  Shaler.    Monograph  XXXIII,  U.  S.  Geol.  Surv.,  57-58. 

t  Geological  observations.    By  Cbas.  Darwin.    216. 

?  G.  K.  Gilbert.  Nat.  Geog.  Mag.,  VIII,  245.  Washington,  1897;  18th  ann.  rep.  U.  S. 
Geol.  Surv.,  pt.  II,  601-«47. 

I  The  great  valley  of  California,  a  criticism  of  isostacy.  By  F.  L.  Ransome.  Bui. 
Geol.  Dept.  Univ.  Calif.,  I,  371-428. 

Earth  movements.  ByC.  R.  Van  Hise.  Trans.  Wis.  Acad.  Sci.,  XI.  Theory  of  isos- 
tacy on  pp.  469-475  and  foot-note ;  478.  Madison,  1898. 

The  connection  of  the  glacial  period  with  oscillations  of  the  land,  especially  in  Scan- 
dinavia. By  Dr.  N.  O.  Hoist.  Geol.  Mag.,  May  1900,  VIII,  205-216. 


179 


180  ORGANIC   AGENTS. 


ORGANIC  AGENCIES,  OR  THE  WORK  OF  ORGANISMS  IN 
GEOLOGY. 

Organic  agencies  are  destructive,  preservative  or  protective,  and  constructive. 

1.  Destructive  organic  agencies  are  those  that  produce  or  hasten  rock 

decay,  such  as  organic  acids. 

2.  Preservative  agencies  are  those  that  protect  rocks  from  destruction, 

such  as  seaweeds  and  mollusks,  that  prevent  waves  from  cutting 
the  shores. 

3.  Constructive  agencies  are  those  that  form  new  rocks,  such  as  peat 

from  plants  and  limestone  from  coral. 


I.  Destructive  Organic  Agents. 

Decay  of  plants  and  animals  produces  humic  acids  that  attack  minerals.* 
The  streams  of  southern  Florida  are  charged  with  carbon  dioxide  from 
decaying  vegetation,  and  as  they  pass  through  and  over  the  lime- 
stones the  waters  attack  and  dissolve  them  rapidly  .t 
Roots  of  plants. 

Roots  etch  the  rocks. 

Sachs'  experiments  on  marble  slabs. 

Roots  pry  rocks  apart.* 

Ivy  prying  boards  from  the  sides  of  houses. 
Sidewalks  lifted  by  the  roots  of  trees. 
Water  follows  down  roots. 

(Luther  Wagoner,  of  San  Francisco,  tells  of  several  roots  of  pine,  or 
some  other  conifer,  %  inch  in  diameter,  found  60  feet  below  the  surface 
of  the  ground  in  a  mine  in  Nevada  county,  California;  rocks  decayed.) 
General  tendency  of  plant  roots  to  break  up  rocks  and  minerals. 
The  decay  of  roots  produces  destructive  organic  acids. 

Roots  penetrate  more  deeply  in  arid  regions. § 
Liverworts. 
Sea-urchins  bore  holes  in  the  hardest  rocks. 

Example  from  the  coast  of  Brazil.     (See  Plate  XII,  opp.  p.  172.) 

*  A.  A.  Julien.    Proc.  A.  A.  A.  S.,  1879,  XXVII,  324. 

Rock,  rock-weathering,  and  soils.  By  G.  P.  Merrill.   190,  foot-note.  -  Merrill.  Jour.Geol., 

189o,  IV,  856. 

t  The  topography  of  Florida.    By  N.  S.  Shaler.    Bui.  Mus.  Comp.  Zool.,  XVI,  144-145. 
t  Notes  on  the  geology  of  the  Bahamas.    By  J.  I.  Northrop.    Trans.  N.  Y.  Acad.  Sci.,  X, 

15-16.    New  York,  1891. 

I  The  conservation  of  soil  moisture.  By  E.  W.  Hilgard  and  R.  H.  Loughridge.   Bui.  121, 
t4"7-"Hilgard  "*  Loughridge'    Rep.  Agr.  Exp.  St.. 


181 


182 


ORGANIC   AGENTS. 


Fig.  41.— Hard  rock  bored  by  sea-urchins.    From  the  coast  of  Brazil. 

Boring  mollusks,  Lithodomus  and  Pholas,  bore  rocks. 

Examples  from  the  coast  of  California. 
Burrowing  insects,  ants  of  the  tropics.* 
Worms,  t  • 

Other  burrowing  animals. 

Rabbits,  squirrels,  ground-hogs,  gophers,  let  in  water  and  gases. 

Crayfish  on  canals  and  rivers. 

Some  cause  levee  breaks  of  the  Mississippi. 


Fig.  42.— Mounds  made  by  ants  in  the  state  of  Minas,  Brazil. 

*  Decomposition  of  rocks  in  Brazil.     By  J.  C.  Branner.     Bui.  Geol.  Soc.  Amer.,  1895,  VII, 

295. 
Ants  as  geologic  agents  in  the  tropics.    By  J.  C.  Branner.    Jour.  Gcol.,  Mar.  1900,  VIII, 

151-153. 
t  Vegetable  mould  and  earthworms.    By  Chas.  Darwin.    New  York,  1882. 


183 


184  ORGANIC    AGENTS. 

II.  Preservative  Work  of  Organic  Agents. 

Protection  of  coasts  by  animals. 

Corals,  serpulse,*  and  mussels. t 
Protection  by  plants.* 

Seaweeds  ;§  corallinese  (calcareous  seaweeds). 

Mangrove  swamps  of  the  tropics, ||  5  to  20  miles  wide.     (Plate  XIII.) 

Bamboos  of  the  Amazonas  break  the  force  of  the  current. 

Bushes  generally  along  stream  and  lake  shores. 

Water  hyacinth,  introduced  in  Florida  in  1890,  helps  to  check  streams 
and  to  check  scour,  and  to  cause  deposition.  IT 

Plants  on  dunes  prevent  the  blowing  of  sand. 

Roots  of  willows  on  canals  and  creeks  prevent  wash. 

Turf  protects  soil  from  wash,  and  rocks  from  exposure  and  decay. 

Forests  on  mountain  slopes  prevent  snowslides  and  landslides. 

Forests  generally  prevent  the  rapid  melting  of  snow  in  the  spring ;  pre- 
vent rapid  flow  of  rain  waters,  and  thus  decrease  floods  and  ero- 
sion. 

III.  Constructive  Organic  Agents. 
Deposits. 
Plants. 

Carbonaceous:  sphagnum,  peat,  lignite,  coal,  oil,  gas. 

Sulphurous. 

Ferruginous:  iron. 

Nitrogenous:  nitre. 

Siliceous:  diatoms  (algee),  chert,  ooze,  eilicified  wood. 

Calcareous:  corallinese  of  the  algse. 
Animals. 

Calcareous:  corals,  shells,  bones,  ooze. 

Siliceous:  sponges,  radiolaria.** 

Phosphatic:  guano,  bones. 


Plants  as  Constructive  Organic  Agents. 

Carbonaceous  deposits. 

The  rocks  of  carbonaceous  plant  origin  are  as  follows  (note  relations 
of  oxygen  and  carbon) : 

*  A.  Agassiz.    Bui.  Mus.  Comp.  Zool.,  XXVI,  253-272. 

t  Across  America  and  Asia.    By  R.  Pumpelly.    188.    London,  1870. 

J  The  conservative  action  of  animals,  etc.     By  W.  A.  Hardman.     Proc.  Liverpool  Geol. 

Soc  ,  1889,  V,  46-51. 
?  Phyllospadix  as  a  beach  builder.    By  R.  E.  Gibbs.     Am.  Nat.,  Feb.  1902,  XXXVI,  101- 

110. 
|  Fresh-water  morasses.    By  N.  S.   Shaler.     10th  ann.  rep.  U.  S.  Geol.  Surv.,pt.  I,  291. 

Washington,  1890.- A.  Agassiz.    Bui.  Mus.  Comp.  Zool. ,300,  XXVI,  53.    Cambridge, 

II  The  water  hyacinth  ...  in  Florida.    Bui.  18.    Bot.  Div.  U.  S.  Dept.  Agr.   Washington, 

1897.—  E.  de  Beaumont.    Geologic  Pratique.    II,  165. 
**  Geikie's  Text  book  of  geology.    439.    3d  ed.    London  and  New  York,  1893. 


185 


186  CARBONACEOUS    DEPOSITS. 

Rocks  of  carbonaceous  Oxygen,  Carbon, 

plant  origin.  percentage.  percentage 

(Wood 44  49) 

1.  Peat 30-40  59 

2.  Lignite 20-35  68 

3.  Bituminous  coal 10-15  81 

Anthracite  coal l%-%/4 95 

4.  Graphite 0  100 

5.  Diamond 0  100 

Petroleum,  asphalt,  gas,  and  related  carbonaceous  minerals,  are  derived  by 

distillation  from  organisms,  but  probably  not  from  any  one  kind.* 
The  carbonaceous  parts  of  rocks  are  derived  from  either  plants  or  ani- 
mals —  chiefly  from  plants. 
Wood  contains  49%  carbon  and  44%  oxygen  (+  6%  hydrogen). 

PKAT.f 

Peat  is  woody  matter  that  has  lost  oxygen,  and  is  thus  altered  part  way 

to  lignite. 

Antiseptic  property  of  peat  prevents  decay. 
Peat  made  of  mosses  (sphagnum)  grows  in  marshes,  and  floats  on,  and  fills, 

shallow  ponds. 

Moss  dies  below,  grows  above;  generations  of  plants. 
Changes  at  bottom  to  brownish  black,  cheese-like  muck. 
Penetrated  by  roots  of  plants  growing  over  surface. 
Covers  large  areas,  5  to  50  feet  thick. 
Rate  of  growth  varies  with  conditions;  1  foot  in  5  to  10  years. 

Some  of  the  European  bogs  have  grown  in  1800  years,  and  have  stumps, 
roads,  coins,  etc.,  beneath  them.     These  bogs  have  grown  from 
one  inch  to  several  feet  per  century. 
Extent. 

Peat-bogs  cover  one-seventh  of  Ireland  4 

The  moss  of  Shannon,  Ireland,  is  50  miles  long  and  from  2  to  3  miles 

wide. 
Dismal  Swamp  of  Virginia  and  North  Carolina  contains  300  square 

miles  of  peat-bog. 

Sol  way  moss  in  northwest  England,  near  Scotland,  7  miles  across. 
In  Norfolk,  England,  500  square  miles  of  peat;  clay  and  sand  separate 

the  beds. 

United  States  and  Canada  to  Montana ;  New  England. 
Bursting  of  peat-mosses  or  peat-bogs. 

Peat-bogs  become  water-logged,  burst,  and  flow.§ 

*  The  production  of  an  asphalt  by  the  distillation  of  a  mixture  of  fish  and  wood.  By  W.  C. 

Day.    Proo.  Am.  Phil.  Soc.,  1898,  XXXVII,  171. 
t  The  formation  of  peat-mosses.    By  Hampus  von  Post.     Bui.  Geol.  Inst.  Univ.  Upsala, 

1892-93, 1,  284.-  G.  Hellsiner.    II,  345. 

On  peat  and  its  uses.    By  T.  S.  Hunt.    Canadian  Naturalist,  Dec.  1864,  2d  ser.,  I,  436-441. 
1  Geikie's  Text-book.    480.    3d  ed.    London  and  New  York,  1893. 
I  Nature.    Jan.  14,  1897,  LV,  254-256;  Jan.  21,  1897,  LV,  268. 


187 


188  CARBONACEOUS    DEPOSITS. 


LIGNITE. 

Lignite,  or  brown  coal,  is  common  in  rocks  of  Tertiary  and  Cretaceous  age. 

Appears  to  be  a  further  change  of  peat. 

Change  takes  place  very  slowly  and  can  not  be  observed. 
Evidences  of  peat  origin  of  lignite. 

1.  Spores  found  in  lignite  like  those  in  peat. 

2.  Plant  impressions  the  same  in  peat  and  lignite. 

3.  Intergadation  of  peat  and  lignite. 

4.  Clays  beneath  lignite  contain  roots  like  those  penetrating  the  clays 

beneath  peat. 

5.  Experimental  demonstration.* 
Interbedding  of  lignite  and  sediments. 

Sections  often  show  several  beds  of  each. 

Must  have  been  flooded ;  or,  if  there  are  marine  fossils,  the  peat-moss 
must  have  been  covered  by  the  sea. 

BITUMINOUS  COAL.* 

Intergradation  of  lignite  and  bituminous  coal. 

Change  very  slow ;  not  in  man's  time. 
Coal  not  derived   from    marine    plants,    for    fucoids    contain  75   to  80% 

water. 
Coal  usually  has  clay  below,  with  roots  penetrating  it. 

Stumps  found  standing;  in  some  cases  these  stems  extend  into  the 

overlying  clays. t 
Sediments  interbedded  with  the  coal  show  changes  by  submergence  and 

new  growths. 
Splitting  of  coal  beds  accounted  for.J 

ANTHRACITE  COAL. 

Daubree's  experiments  with  wood.§ 

Changed  form  of  bituminous  coal. 

Plants  preserved  as  coal  in  some  cases. 

Relations  of  the  anthracite  fields  of  Pennsylvania  to  the  bituminous 
ones  of  the  same  state. 

Change  in  the  upper  ends  of  synclines  at  Forest  City,  above  Carbon- 
dale. 

Ultra  change  of  Rhode  Island  anthracite.  || 

*  See  abstract  of  work  of  Adams  and  Nicolson.     Science,  Jan.  21,  1898,  new  ser.,  VII,  83. 
Vegetable  origin  of  coal.    By  Leo  Lesquereux.    Ann.  rep.  Geol.  Surv.  Penn.,  1885,  pp.  95- 

124.    Harrisburg,  1886. 

t  Coal  plants,  etc.    By  W.  S.  Gresley.    Geol.  Mag.,  Dec.  1900,  VII,  538-544. 
t  Lapparant.    Traite"  de  ge"ologie.    841.    Paris,  1885. 

g  Les  eaux  souterraines  aux  e~poques  anciennes.    Par  A.  Daubr^e.    297     Paris,  1887. 
||  On  the  origin  of  anthracite.      By  E.  T.  Hardman.      Jour.  Roy.  Geol.  Soc.  Ireland,  IV, 

new  ser.,  200-209.     Edinburg,  1877. 


189 


191 


192  CARBONACEOUS    DEPOSITS. 

Theories  advanced  to  explain  the  origin  of  coal. 

1.  Marine  plants. 

Marine  plants  have  no  wood,  but  cellular  tissue  only. 

2.  Blown  into  lakes  from  the  land. 

Too  widespread ;  area  of  North  American  coal  fields. 

3.  Floated  timber  of  deltas. 

'    Too  much  and  too  widespread ;  the  coal  beds  are  of  rather  even 
thickness;  driftwood  irregular  and  mixed  with  mud. 

4.  Timber  floated  into  the  sea. 

Stumps  beneath  the  coal  are  rooted  in  place. 

5.  Peat-bog  theory  of  origin  now  accepted.* 

Carbon  from  the  air. 

Renewed  from  the  crystalline  rocks  and  from  the  sea. 

Air  not  necessarily  overcharged  with  carbon. t 

GRAPHITE. 

Graphite  is  produced  in  some  cases  by  a  still  further  change  of  coal. 

Too  much  changed  to  be  available  for  fuel. 

Changed  in  some  cases  by  excessive  heat. 

Found  in  the  oldest  rocks. 

Origin  of  the  graphite  found  in  pig-iron;  derived  from  coal. 

DIAMONDS. 

Diamonds  are  crystalline  forms  of  carbon,  probably  formed  by  change  of 
graphite  by  pressure  and  heat.  Graphite  found  in  the  diamond  ma- 
trix of  Brazil. i 

DRIFT-TIMBER. 

Enormous  quantities  of  drift-timber  washed  down  by  freshets. 

Rafts  in  rivers ;  common  in  delta  regions. 

Atchafalaya,  La.,  raft  10  miles  long  by  700  feet  wide,  8  feet  thick ;  50  years' 

accumulations. § 

Floating  islands  of  the  Amazonas  and  of  the  Paraguay. 
Water  hyacinth  of  Florida. || 

*  Discourses.    Biological  and  geological  essays.    By  Thos.  H.  Huxley.    137-161.     New 

Origin  of  coal. '  By  R.  Dakyus.      Geol.  Mag.,  1901,  p.  135;  Jan.  1901,  VIII,  29-34;   Mar. 

1901,  VIII,  135. 
t  Microscopical  light  in  geological  darkness.  By  E.  W.  Claypole.   Am.  Geol.,  Oct.  1898, 

XXII,  217-228. 

Chamberlin.    Jour.  Geol.,  Oct.  1898,  VI,  609-621. 
On  the  gases  enclosed  in  crystalline  rocks  and  minerals.     By  W.  A.  Tilden.    Chem. 

News,  April  9,  1897. 

|  O.  A.  Derby.    Jour.  Geol..  VI,  121-146.    Chicago,  1898. 
g  The  great  raft.     By  A.  C.  Veatch.    Prelim,  rep.  on  the  Geol.  of  La.,  160-173.     [Baton 

Rouge,  1899.]      " 
||  Bui.  18,  U.  S.  Dept.  Agr.,  Div.  Bot.    Washington,  1897. 


193 


194  DEPOSITS    FROM    PLANTS. 


SULPHUROUS  DEPOSITS  FROM  PLANTS. 

Certain  bacteria  extract  sulphur  from  sulphuretted  water  (sewage  works 
and  factory  effluents)  and  store  it  up  as  globules,  known  to  engi- 
neers as  "  sewage  fungi."* 

In  hot  springs  in  Japan  ;t  temperature  154°  to  157°  Fahr. 
Only  in  water  with  hydrogen  sulphide. 

FERRUGINOUS  DEPOSITS  FROM  PLANTS. 

Iron  carried  in  solution  in  streams  as  carbonate,  loses  CO2  through  the 
agency  of  bacteria,  and  ferric  oxide  is  precipitated. 

NITROGENOUS  DEPOSITS  FROM  PLANTS. 
Nitre  or  saltpeter,  formed  by  nitrifying  bacteria. i 

SILICEOUS  DEPOSITS  FROM  PLANTS. 

Diatoms  are  low  forms  of  microscopic  plants  (alg?e)  living  in  salt  or  fresh 

water.  § 

Abundant  in  fresh  warm  waters  of  Yellowstone  National  Park. 
Temperatures  up  to  185°  Fahr. 
Deposits  there  3  to  6  feet  thick ;  called  "  sinter."  || 
Silica  extracted  from  the  water. 
Deposits  consist  of  accumulations  of  skeletons. 

Marine  diatom  beds  at  Santa  Cruz,  California,  are  700  feet  thick. 
In  Nevada,  200  to  300  feet  thick. 
Rocks  of  diatoms  IT  are  earthy  like  chalk,  harsh   to  the  touch;    used  to 

polish  metals. 

Often  found  in  swamps  beneath  peat. 
Called  tripolite,  tripoli  powder,  infusorial  earth.** 
The  distribution  of  marine  diatom  deposits  in  existing  seas  suggests  that 

they  may  be  cold-water  deposits. ft 

Relations  of  the  diatom  beds  of  California  to  the  petroleum  deposits. 
In  many  places  the  materials  are  altered  to  cherts. 

Silicified  wood  is  not  properly  a  siliceous  deposit  made  by  plants,  but  a  re- 
placement of  wood  by  silica  from  solution. 
Enormous  quantities  in  Yellowstone  region. U     (Plate  XIV.) 

*  Bennett  and  Murray's  Cryptogamic  botany.    454.    London  and  New  York,  1889. 

t  Am.  Nat.,  June  1898,  XXXII,  456-457. 

t  Microbes,  ferments  and  moulds.    By  E.  L.  Trouessart.      121-122.     Internal.  Sci.  Ser. 

New  York,  1892. 

§  A.  M.  Edwards.    Microscopical  Jour.,  1899,  pp.  49-55. 

II  W.  H.  Weed.  9th  ann.  rep.  U.  S.  Geol.  Surv.,  650-676.  Washington,  1889. 
11  On  diatoms,  see  Zittel.  Paleontologie,  pt.  II.  Set  t>cq.  (French  edition.) 
**The  tripolite  deposit  of  Fitzgerald  Lake  near  St.  John,  New  Brunswick.  Tech. 

Quar.,  June  19ul,  XIV,  124-127. 

ft  Maps  of  Mem.      Mus.  Comp.  Zool.,  XXVI,  no.  1.    Cambridge,  1902. 
II  Monograph  XXXII,  pt.  II,  U.  S.  Geol.  Surv.,  755-760,  and  plates. 


Plate  XIV«.  —  Bridge  formed  by  a  petrified  tree  trunk  near  Holbrook,  Arizona. 
(Vroman.) 


Plate  XIV6.  -  Petrified  logs,  Chalcedony  Park,  near  Holbrook,  Arizona.    Petrified 
wood  covers  an  area  of  more  than  a  thousand  acres  at  that  place. 


195 


196  CORAL    REEFS. 


CALCAREOUS  DEPOSITS  FROM  PLANTS. 
Nullipores  or  Corallime  are  coral-like  calcareous  algse  growing  in  salt  water. 

They  help  build  up  coral  reefs  and  coral  sand-beaches. 
Other  calcareous  algse  contribute  to  marine  calcareous  deposits.* 
Calcareous  tufas  of  Great  Basin  formed  through  the  agency  of  low  plant 

life.t 

One  calcareous  spring  in  Yellowstone  Park  (Mammoth  Hot  Spring) ;  de- 
posits made  by  algse. i 

Some  calcareous  oolites  and  marls  are  lime  secretions  of  algse. § 
"  Water-biscuit"  of  Canandaigua  Lake  formed  by  algse  taking  up  CO^  and 
causing  the  precipitation  of  the  lime  from  the  water.|| 


Animals  as  Constructive  Organic  Agents. 

Calcareous  rocks  made  by  animals. 

1.  Corals  and  serpuhe  whose  skeletons  are  attached.  IT 

2.  Shells  of  microscopic  marine  organisms  living  at  or  near  the  water's 

surface;  foraminifera. 

3.  Shells  of  univalves  (gasteropods),  bivalves  (lamellibranchs),  worms, 

echinoderms,  crustaceee,  and  all  animals  having  calcareous  skel- 
etons, whether  vertebrates,  such  as  fishes,  or  invertebrates,  such 
as  crinoids. 

CORAL  REEFS.** 
Importance  of  the  subject. 

1.  Large  areas  of  the  globe  covered  by  coral  reefs  and  islands.     Aus- 

tralian reef  1,250  miles  long  by  10  to  90  miles  wide. 

2.  Coral  makes  much  of  the  lime  rock  of  the  earth. 

*  Proc.  and  Trans.  Nova  Scotia  Inst.  of  Sci.,  IX,  XCII-XCIII,  1897. 

1  1.  C.  Russell.    Bui.  108,  U.  S.  Geol.  Surv.,  94-95.    Washington,  1893. 

t  W.  H.  Weed.    9th  ann.  rep.  U.  S.  Geol.  Surv.,  628-649.    Washington,  1889. 

?  A.  Rothpletz.    Am.  Geol.,  1892,  X,  279-282. 

For  bibliography  of  oolites  see  The  Bedford  oolitic  limestone  of  Indiana.     By  T.  C. 

Hopkins  and  C.  E.  Siebenthal.      21st  ann.  rep.  State  Geol.  Indiana,  397-410.    Ind- 

ianapolis, 1896. 
The  lakes  of  northern  Indiana,  etc.     By  W.  S.  Blatchley  and  G.  H.  Ashley.      25th  ann. 

rep.  Geol.  Indiana,  33,  43-48.    Indianapolis.  1901. 
A  contribution  to  the  natural  history  of  marl.    By  C.  A.  Davis.     Jour.  Geol.,  VIII,  485- 

497;  498-503.    Sept.  1900. 


|  Clarke.    Bui.  N.  Y.  State  Mus.,  VIII,  W5-198.    Albany,  1900. 
11  Some  recent  views  on  the  theory  of  the  formation  of  coral  reefs.    By  A.  Agassiz.    Bui. 
Mus.  Comp.  Zool.,  XXVI,  170-187.    Cambridge,  1894.  —  Nature,  Nov.  10,  1898,  LIX, 

**  The  structure  and  distribution  of  coral  reefs.     By  Charles  Darwin.     3d  ed.    London, 

1889.   • 

Corals  and  coral  islands.    By  James  D.  Dana.    3d  ed.     New  York  [1890]. 
On  the  structure  and  origin  of  coral  reefs  and  islands.     By  John  Murray.     Proc.  Roy. 

Soc.  Edinburg,  1880,  X,  505. 
The  islands  and  coral  reefs  of  the  Fiji  group.      By  Alexander  Agassiz.    Am.  Jour.  Sci., 

Feb.  1898,  CLV,  113-123.  —  Nature,  Nov.  10,  1898,  LIX,  29. 
Some  recent  views  on  the  theory  of  the  formation  of  coral  reefs.     By  A.  Agassiz.      Bui. 

Mus.  Comp.  Zool.,  XXVI,  170-187.    Cambridge,  1894. 


197 


198 


CORAL    REEFS. 


Coral  rocks  are  formed  from  the  skeletons  of  polyps. 

Animals  are  soft,  gelatinous,  often  transparent,  of  various  colors. 

Radiate  structure  with  tentacles. 

Carbonate  of  lime  deposited  in  the  lower  part,  which  is  fixed. 

Form  and  deposition  of  the  lime  by  polyps  are  vital  functions,  and  not 
subject  to  will. 

The  growth  of  coral  reefs  is  produced  by  growth  of  these  deposits. 
Forms  of  corals. 

1.  Loosely  branching. 

2.  Solid,  spherical,  or  hemispherical. 

3.  Tabulate. 
Reproduction . 

1.  By  eggs  having  power  of  locomotion,  and  floating  away  in  the  water 

till  they  attach  themselves  to  the  rocks. 

2.  By  branching  or  budding. 
Conditions  of  growth  of  the  reef-building  corals. 

(Reference  is  made  here  only  to  what  are  known  as  the  reef-building 
corals;  other  corals  live  at  great  depths  in  the  ocean,  and  in 
very  cold  waters,  but  they  do  not  form  reefs.) 

1.  Temperature  at  or  above  70°  Fahr. 

2.  A  range  of  temperature  not  exceeding  12°  Fahr.* 

3.  Depth,  150  feet  and  less;  most  favorable  at  50  feet  and  less. 

4.  Clear  salt  water. 

Effects  of  elevation  and  depression,  mud,  volcanic  ashes,  and  fresh 
water. 

5.  Constant  change  of  water;  necessity  of  lime  and  oxygen. 


Fig.  44.— A  coral  reef  on  the  coast  of  Brazil.    (Hartt.) 
*  Murray  and  Irvine.    Nature,  June  12,  1890,  XLII,  162. 


200  CORAL'  REEFS. 

Forms  of  coral  reefs. 

1.  Fringing:  join  the  land. 

2.  Barrier:  form  barriers  between  sea  and  land. 

3.  Circular:    approximately  circular;    enclose  water;    sometimes  en- 

closed lagoons  fill  up. 
(These  forms  are  not  sharply  distinguishable,  but  merge  into  one 

another.) 
Size  of  coral  reefs. 

The  great  reef  of  Australia  is  1,250  miles  long  by  10  to  90  miles  wide. 
Theories  of  reef  formation. 

1.  Subsidence  theory  of  Darwin. 

a.  Intergration  of  reef  forms. 

b.  Actual  subsidence  of  some  existing  islands. 

c.  Depths  at  which  reef  rocks  are  found. 

A  bore-hole  sunk  in  1897,  at  Funafuti,  northeast  Australia, 
passed  through  987  feet  of  coral  without  reaching  the 
bottom  of  the  reef.* 

d.  Elevation  of  some  reefs. 

For  depression  is  as  common  as  elevation. 

2.  Murray's  theory  of  submarine  peaks. 

Conditions. 

a.  That  the  coral  polyps  take  possession  of  submarine  peaks. 
6.  That  when  the  depth  is  too  great,  accumulations  of  micro- 
scopic organic  remains  build  up  the  peaks  till  they  come 
within  reach  of  the  corals. 

Murray  thinks  atolls  grow  larger  by  building  be}rond  the  growing  depth. 
Darwin  thinks  atolls  grow  smaller. 
Murray's  theory  is  not  improbable. 
Rate  of  growth  of  reefs. 

Can  be  determined  by  observation. 

Agassiz's  estimate,  1  inch  in  8  years,  or  1  foot  in  a  century. 

Others  estimate  2  feet  in  a  century. 

Coral  987  feet  deep  is  837  feet  below  growing  depth  for  living  corals. 

At  2  feet  in  a  century  it  would  require  41,850  years  for  the  reef  to 

attain  the  thickness  of  837  feet  below  the  level  of  growth. 
Change  by  crystallization  from  original  form. 

All  fossil  reefs  must  have  grown  under  more  or  less  similar  conditions 

of  depth  and  temperature. 
Reefs  at  the  falls  of  the  Ohio. 
Tertiary  reef  near  Bainbridge,  Georgia, t  and  on  the  island  of  Oahu.J 

*  Nature,  Dec.  9,  1897,  L  VII,  137;  Mar.  24,   1898,  LVII,  494-495;   July  7,  1898,  LVIII,  221; 

Nov.  10,  1898,  p.  29.  —  Proe.  Roy.  Soc.  N.  S.  W.,  Oct.  5,  1898,  p.  IV. 
In  opposition  to  the  theory  of  subsidence,  see  A.  Agassiz  in  Am.  Jour.  Sci.,  Feb.  1898,  V, 

113-123;  and  same  for  Aug.  1898,  VI,  165-167.    Bui.  Mus.Comp.  Zool.,  XXVI,  170-187. 
t  T.  W.  Vaughan.     Science,  Dec.  7,  1900,  pp.  873-875. 
|  W.  H.  Dall.    Bui.  Geol.  Soc.  Am.,  XI,  57-60. 


201 


202  .  DEPOSITS    FORMED    BY    MARINE    ANIMALS. 

Possibility  of  other  conditions. 

Temperatures  are  constantly  lowering. 

Life  began  in  warm  seas  and  climates. 

The  tendency  is  to  adapt  to  colder  conditions,  rather  than  to  originate 

in  cold  climates,  and  to  change  from  colder  to  warmer. 
Coral  reefs  teach  that  — 

1.  Coral  limestone  is  made  by  animal  growths,  assisted  by  wave  work 

and  consolidation. 

2.  Coral  limestones  are  of  marine  shallow-water  origin. 

3.  They  attain  great  thickness  by  subsidence. 

4.  Our  limestones  contain  near-shore  life,  and  are,  therefore,  of  near- 

shore  and  shallow-water,  rather  than  of  deep-sea  origin. 

SERPUL*:.* 
MICROSCOPIC  MARINE  ANIMALS. 

Foraminifera  have  (mostly)  calcareous  skeletons. 
Live  near  surface  of  seas.t 

Dying,  their  skeletons  sink  to  bottom,  forming  "ooze.1' 
Chalk  made  up  of  such  calcareous  skeletons. 
Skeletons  found  to  depths  of  13,800  feet.* 

Below  that  depth  these  skeletons  are  dissolved  by  pressure  and  the 

carbon  dioxide  in  the  water. § 
Bryozoa  lenses  of  limestone. || 

MOLLUSCAN   AND  OTHER  CALCAREOUS   SHELLS   AND   SKELETONS. IT 

(Worms,  echini,  crabs,  crinoids,  etc.) 

Examples:  coquina  of  Florida ;  conch  shells  on  the  Bahamas.** 

Encrinital  limestone. 
Siliceous  deposits  formed  by  animate. ft 
Spicules  of  sponges  accumulate. 

Form  cherts,  flints,  or  hornstones. 

Extensive  deposits  of  chert  in  Missouri,  Tennessee,  Arkansas,  Eng- 
land, etc. 

The  cherts  of  California  are  derived  largely  from  the  skeletons  of 
diatoms. 

*  A.  Agassiz.    Bui.  Mus.  Comp.  Zool.,  XXVI.  253-272,  and  plates  XXTT,  XXIII,  XXVI. 

tOp.  cit.,56. 

t  On  foraminifera  see  Zittel's  Text-book  of  paleontology,  Eastman's  translation.  Vol.  I, 

pt.  I,  18-37.    London  and  New  York,  1896.      Has  bibliography. 
The  Atlantic.    By  C.  Wy  ville  Thomson.    I,  199-203,  249.    New  York,  1878. 
Discourses.    Biological  and  geological  essays.    By  T.  H.  Huxley.    1-36.   New  York,  1897. 
'i  See  also  Dittmar,  in  Challenger  reports.    Physics  and  chemistry.    I,  222. 
\  Reef  structures  in  Clinton  and  Niagara  strata  of  western  New  York.     By  C.  J.  Sarle. 

Am.  Geol.,  Nov.  1901,  XXVIII,  282-299. 
1i  Mechanically  formed  limestones  from  Junagarh  and  other  localities.       By  J.   W. 

Evans.    Quar.  Jour.  Geol.  Soc.,  LVI,  559-583. 

Derived  limestones.    By  J.  W.  Sollas.    Geol.  Mag.,  June  1900,  pp.  248-250. 
**  Agassiz.    Op.  cit.,  70. 

tt  Zittel's  Paleontology,  Eastman's  translation.    I,  pt.  I,  42  et  seq. 
Colloid   silica.    Jukes-Brown  and  Hill.    Quar.  Jour.  Geol.  Soc.,  Aug.  1889,  XLV,  403. 
On  fossil  sponges  of  the  flint  nodules  in  the  Lower  Cretaceous  of  Texas.  By  J.  A.  Merrill. 

Bui.  Mus.  Comp.  Zool.,  July  1895,  XXVII,  1-26. 
Review  Am.  Geol.,  Jan.  1896,  XVII,  52-53. 
Keyes.    Am.  Jour.  Sci.,  Dec.  1892,  CXLIV,  451. 
Hovey.    Am.  Jour.  Sci.,  Nov.  1894,  CXLVIII,  401. 
Lawson.    loth  U.  S.  Geol.  Surv.,  1895,  p.  420. 


203 


204  MAN    AS   A    GEOLOGIC    AGENT. 


PHOSPHATIC  DEPOSITS  FORMED  BY  ANIMALS. 

Droppings  and  bones  of  marine  animals  or  birds. 
Accumulate  on  sea  bottom  or  on  arid  land. 
Guano  on  the  islands  of  Peru  in  an  arid  region. 

No  rain  to  wash  it  away.* 
Phosphate  rocks  of  Tennessee  and  Arkansas. 
Sometimes  concentrated,  as  in  the  rivers  of  South  Carolina. 
Marine  organisms  are  most  abundant  in  shallow  waters  and  near  shore. 
This  is  especially  true  in  the  tropics.     In  polar  regions  the  fauna  is 
more  abundant  in  depths  of  50  to  150  fathoms  than  in  depths  of  less 
than  50  fathoms.* 

We  have  now  gone  over  all  the  different  methods  by  which  rocks  are  made. 
All  rocks  fall  under  one  of  these  heads,  and  are  made  in  one  of  these  ways. 
/  Mechanical  sediments  deposited  in  water,  or  by  wind. 
All  rocks  have         I  Chemical  deposits,  deposited  from  solution, 
originated  as  \  igneous  rocks  from  fusion. 

I  Organic  deposits  made  by  plants  and  animals. 

All  these  deposits  are  subject  to  metamorphisms  and  change  of  position  of  bed- 
ding.    (See  Structural  Geology,  Part  IV.) 


Man  as  a  Geologic  Agent.; 

Man's  work  is  confined  to  modifying  the  operations  of  nature. 
Of  comparatively  little  importance,  because  the  element  of  time  is  wanting 
for  his  works. 

1.  Man's  influence  on  plants  and  forests. 

2.  Man's  influence  on  animals. 

3.  Man's  influence  on  land  changes. 

MAN'S  INFLUENCE  ON  PLANTS. 

Domesticated  and  cultivated  plants,  formerly  all  wild. 
Distributed  over  the  world  by  man  intentionally. 
Examples:  wheat,  oats,  rye,  beans,  corn. 
Potatoes  only  since  the  discovery  of  America. 
Cocoanuts,  bananas,  date-palms,  rice,  sugar-cane,  cotton,  coffee, 

oranges,  in  warm  climates  only. 

Ornamental  plants  imported  and  scattered  by  dealers. 
Forest  trees. 

Examples :  eucalyptus  and  palms. 

*  Note  on  Clipperton  atoll.     By  W.  J.  Wharton.     Quar.  Jour.  Geol.  Soc..  LJV,  228-229. 

London,  1898. 

t  Murray.    Nature,  Mar.  25,  1897,  p.  501. 

I  The  earth  as  modified  by  human  action.    By  G.  P.  Marsh.    New  York,  1885. 
^'influence  de  1'homme  sur  la  terre.  Par  A.  Woeikof.   Ann.  de  Geographic,  15  Mars  1901, 

•10e  an.,  97-114;  15  Mai  1901,  pp.  193-215. 


205 


206  MAN  AS  A  GEOLOGIC  AGENT. 

Other  plants  accidentally  distributed. 
Tumbleweed,  Russian  thistle. 
Weeds  along  roads  and  railways.* 
Cockle  in  wheat. 

MAN'S  INFLUENCE  ON  THE  FORESTS. 
By  planting. 

Eucalyptus,  introduced  from  Australia;  Lombard}-  poplars  from  Europe. 

In  Switzerland,  forests  planted  to  prevent  avalanches. 

On  the  west  coast  of  France,  for  resin  and  to  stop  the  shifting  of  sand- 
dunes. 

Willows  planted  on  canals  and  streams  to  prevent  cutting. 

To  prevent  landslides. 
By  cutting  away. 

Destruction  of  forests  for  lumber,  charcoal,  tan-bark. 

Destruction  by  forest  fires ;  by  grazing. 

1.  Effects  of  forests  on  the  scour  of  streams. 

Cutting  of  bamboos  along  streams  permits  scour. 

Cutting  mangrove  swamps  permits  scour  of  the  coast :  no  filling. 

2.  Effects  of  forests  on  floods  by  — 

Holding  back  water  in  leaves  and  debris. 
Holding  back  snow  from  melting  rapidly. 

3.  Removal  of  forests  exposes  the  soil  to  sun  and  drouth,  and  it  cracks 

and  lets  in  decomposing  agents. 

Questions  to  be  considered. 
Do  forests  change  climate? 
What  is  climate? 
Annual  variations. 
Long  series  of  observations  necessary  to  determine  the  climate. 

MAN'S  INFLUENCE  ON  ANIMAL  LIFE. 

Some  animals  cared  for  and  domesticated. 
Others  decimated  or  exterminated. 

I.  Animals  preserved  and  distributed  voluntarily. 

Horses,  sheep,  camels,  cows,  pigs,  chickens,  geese,  bees. 

Preservation  of  game. 

Oysters  planted  in  brackish  water. 

Fishes  hatched  and  distributed  over  the  country. 

Slavery. 

Africans  carried  to  America. 

Mingling  of  European,  American,  African,  and  Asiatic  races. 

Mingling  of  races  in  South  America  through  the  enslavement  of 
Africans  and  aborigines. 

*  The  water  hyacinth.      Bui.  18,  U.  S.  Dept.  Agr.,  Div.  Hot.      Washington,  1897. 
Tumbling  mustard.    Circular  no.  7,  U.  S.  Dept.  Agr.,  Div.  Hot.     Washington,  1896. 


207 


208  MAN  AS  A  GEOLOGIC  AGENT. 

II.  Animals  distributed  involuntarily. 

1.  Injurious  or  parasitic  insects. 

Colorado  potato-beetle. 

Hessian  fly. 

Scale  insects  imported  on  fruit. 

Of  73  injurious  insects  of  primary  importance  in  the  United  States, 

37  are  introduced,  all  but  one,  accidentally.* 
Gipsy-moth,  introduced  in  1869  in  Massachusetts,  has  cost  a  million 

dollars,  and  will  cost  one  and  a  half  millions  more  to  get  rid 

of  it. 

2.  Harmless  animals  developing  into  pests. 

English  sparrows  in  United  States  since  1850-67. 
Parrots  of  Australia. 
Rabbits. 

Marine  life  likely  to  be  modified  by  the  Suez  canal  and  the  Panama 
canal. 

III.  Animals  exterminated,  or  nearly  so. 

1.  Dangerous  or  injurious:  squirrels,  snakes,  panthers. 

2.  Game  valuable  for  food,  fur,  or  hides. 

Bears,  beavers,  buffaloes,  whales,  fur-seals. 

3.  Wanton  destruction. 

Birds  of  the  guano  islands. 
Buffaloes. 

IV.  MAN'S  INFLUENCE  ON  THE  LAND. 
Reclaiming  land. 

Marshes  and  swamps  drained  (elevated  marshes). 

Sea  marshes  of  Holland. 

Lowering  Swiss  lake  for  land. 

Raising  river  banks. 

Levees  of  the  Po  bring  it  above  the  farms. 
Levees  of  the  Mississippi. 
Protection  of  land. 

From  the  sea  by  dikes  and  sea-walls. 

Example:  Holland,  extensive  works. 

From  streams,  by  paving  and  straightening  channels. 
Modification  of  land. 

By  building  dams  and  reservoirs  that  silt  up. 

By  cutting  bars,  dredging  basins. 

By  cutting  timber  from  sandy  lands  and  thus  starting  dunes. 

By  planting  on  dunes  and  stopping  them. 

By  irrigation :  Egypt,  Spain,  California. 
Placer  mining. 

Method  of  work,  and  amount  of  earth  washed  down. 

Fills  streams  and  overflows  valleys. 

*  Spread  of  land  species  by  the  agency  of  man.    By  L.  O.  Howard.     Science,  Sept.  10, 
1897,  new  ser.,  VI,  r1  — 


209 


210 


MAN    AS    A    GEOLOGIC    AGENT. 


Cultivation  of  the  soil* 

Cultivation  greatly  increases  chemical  activity  in  soil. 

1.  Erosion  hastened;  ground  not  protected  by  plants. 

2.  Erosion  is  checked  where  the  land  is  terraced,  as  in  Switzerland. 
Checking  stream  erosion. 

Mattrasses  and  piles  at  Pine  Bluff,  Arkansas. 
Levees  of  the  Mississippi  river,  confining  it  to  channel. 
Straightening  and  paving  the  Rhone  and  other  swift  streams  in  Switzer- 
land. 
Using  the  falls  for  power  and  thus  checking  the  cutting. 

Example :  Niagara  Falls. 
Future  water  storage. 

Will  prevent  or  check  floods,  and  retard  erosion. 
Geological  deposits  made  by  man. 

Refuse  heaps  about  cities  and  towns. 

Those  of  large  cities  dumped  into  the  sea  from  scows  and  ships. 
Cities  buried. 

By  dust-storms  of  Africa. 
Sand-dunes  of  Bermuda. 
Volcanic  dust  of  Vesuvius. 

Example :  Herculaneum  and  Pompeii. 
Ocean  deposits  are  receiving  the  rejectamenta  of  civilization  and  preserving 

them  as  fossils. 
Distribution  over  the  entire  globe  by  means  of  navigation. 

*  The  economic  aspects  of  soil  erosion.     By  N.  S.  Shaler.     Nat.  Geog.  Mag.,  Nov.  1896, 
VII,  36&-S77. 


211 


212 


SEDIMENTARY    ROCKS. 


PART    II. 


STRUCTURAL  GEOLOGY,  OR  THE  MODIFICATION  OF  ROCKS. 

Structural  Geology  treats  of  the  kinds  and  arrangements  of  rocks,  and 
the  changes  to  which  they  are  subject. 

Rocks  are  any  materials  forming  the  earth's  crust. 

They  are  (1)  sedimentary  or  stratified;  (2)  igneous  or  unstratified;  and 
(3)  vein  deposits. 


SEDIMENTARY,  OR  STRATIFIED  ROCKS. 


UNCONSOLIDATKD.    CONSOLIDATED. 


'••    - 

'  Shingle. 

Breccia.* 

Arenaceous, 

Gravel. 

Conglomerate, 

or  sandy. 

pudding-stone. 

^Ssind. 

Sandstone, 

(  Shallow-water 

or  quartzite. 

deposits.                Argillaceous, 

Clay. 

Shale, 

or  clayey. 

or  slate. 

Calcareous, 

Oozie, 

Chalk,  limestone, 

or  limy. 

shells. 

marble 

Stratified 
rocks.    < 

Deep-water 
deposits,    600 
feet  and  over. 

Tufaceous. 
1  Skeletal- 

Cinders, 
ashes. 
Ooze, 

Tuff. 
Diatom  shale,  flint, 

siliceous. 

(silic- 

chert, jasper. 

eous). 

r  Carbonaceous. 

Peat. 

Lignite,  coal. 

1  Arenaceous. 
t  Land  deposits.       J 
1  Argillaceous. 

Sand. 

Clay. 

jEolian  sandstone. 
Loess. 

t  Tufaceous. 

Cinders. 

Tuff. 

*  llth  ann.  rep.  U.  S.  Geol.  Surv.,319,  320,  321.  —  Monograph  XXVIII,  U.  S.  Geol.  Surv., 
plates  VIII,  XXVI. 

Arthur  Winslow.      Lead  and  zinc  deposits  of  Missouri.      464-467.      Jefferson  City,  1894. 

Branner.    Zinc  and  lead  region  of  Arkansas.    21-23.    Little  Rock,  1900. 

Gordon.    Jour.  Geol.,  Ill,  307.    Chicago,  1895. 

On  the  relation  of  certain  breccias,  etc.     By  T.  G.   Bonney.     Quar.  Jour.  Geol.  Soc., 

LVIII,  185-206.    London,  May  1902. 
On  a  remarkable  inlier  among  the  Jurassic  rocks,  etc.     By  J.  F.  Blake.     Quar.  Jour. 

Geol.  Soc.,  LVIII,  296-312.     London,  May  1902. 


I 

y 


<f~ 


Plate  XV.  —  Brecciated  siliceous  limestone  cemented  with  dolomite  spar. 


213 


214 


SEDIMENTARY    ROCKS. 


Sedimentary  rocks  cover  nine-tenths  of  the  land,  and  all  of  the  sea 
bottom. 

They  average  several  miles  in  thickness,  with  a  maximum  thickness 
of  twenty  miles. 

Sedimentary  rocks  may  be  hard  or  soft;  there  is  no  line  of  demarka- 
tion  between  the  consolidated  and  the  unconsolidated. 

There  is  no  sharp  line  of  demarkation  between  the  materials  of  these 
rocks ;  they  all  intergrade. 


7>a.  -JL. I M eVtone^ 


Fig.  45.— Breccia  of  dolomite,  zinc  blende  and  dolomite  spar  (natural 

The  forms  of  deposits  are  determined 
by  the  origin  of  the  materials,  and  by 
the  place  and  manner  of  deposition. 
The  rock  masses  are  known  by  various 
names,  such  as  layers,  beds,  strata,  veins, 
dikes,  deposits,  formations,  etc.,  all  of 
which  are  rather  loosely  applied. 

BEDDING. 

Stratified  rocks  are  laid  down  in  beds,  ^Ei 

or  approximately  parallel  layers. 

ej     4  Fig.  46.-Diagram  illustrating  a  meth- 

btratum  (plural  strata),  beds,  layers,     od  of  breccia-making.    (Chamberlin.) 


a 


215 


216 


SEDIMENTARY    ROCKS. 


Lamina,  a  very  thin  layer. 

Lenticular  beds  are  lens-shaped. 

False  bedding,  or  plunge  and  flow  structure,*  is  characteristic  of  nearly 

all  coarse  sediments. 

Produced  by  wind-bedding  in  any  kind  of  materials. 
Conformity. 

Rocks  conform  to  each  other  (or  are  conformable)  when  laid  down  in 

successive  layers  in  a  continuous  deposition. 
Unconformity  indicates  interruption^     (See  Plate  XVI.) 


Fig.  47.— An  unconformity  (&)  between  Tertiary  (c)  and  later  (a)  beds.    (Harris.) 

Impressions  during  deposition. 

Ripple-marks  are  found  in  sediments  in  the  bottom  of  rather  shallow 

water. 

They  are  made  by  the  vibration  of  the  water  up  to  a  depth  of  450  feet.t 
Ripple-marks  are  visible  on  the  bottom  of  Lake  Geneva,  caused  by  the 

paddle-wheels  of  steamers. 
Giant  ripples  caused  by  wave  interference  in  shallow  water. § 


Fig.  48.— Ripple-marks  in  loose  sands  exposed  at  low  tide. 

*  Dutton's  High  plateaus  of  Utah.     152,  208.     Washington,  1880. 

Ann.  rep.  Geol.  Surv.  Iowa.    VII,  plate  p.  218.    Des  Moines,  1897. 

t  Ann.  rep.  Geol.  Surv.  Iowa.    V,  plate  I,  opp.  52.    Des  Moines,  1896. 

Univ.  State  N.  Y.  State  Mus.  Rep.  49,  1895.    444. 

t  Lapparent     Trait6  de  Geologic.    254.    Paris,  1900. 

Sorby.    The  Geologist,  II,  137-147.     London,  1859. 

Bui.  19,  vol.  IV,  N.  Y.  State  Mus.,  172. 

Rippelmarken.    Inaug.  Diss.  von  ErnsfBertololy.    Frankenthal,  1894. 

V.  Cornish.    Geog.  Jour.,  XVIII,  170-202;  July-Dec.  1901.—  Scot.  Geog.  Mag.,  Jan.  1901. 

Nature,  Apr.  25,  1901,  pp.  623-625. 
I  G.  K.  Gilbert.    Bui.  Geol.  Soc.  Am.,  X,  135-140. -Fairchild.   Am.  Geol.,  XXVIII,  9-14. 

Branner.    Jour.  Geol.,  IX,  535-536. 


217 


218  SEDIMENTARY    ROCKS. 

Rain-prints. 

Sun-cracks. 

Tracks  of  birds  and  other  animals.* 

Fossils  are  the  hard  parts,  or  impressions,  of  animals  or  plants  that  die 

in  the  water,  or  are  washed  down  from  the  land. 
Alternation  of  beds  is  produced  by  the  — 

1.  Varying  conditions  of  supply. 

2.  Changes  of  currents. 
Persistence  of  strata. 

Some  strata  extend  for  hundreds  of  miles. 

Beds  are  more  likely  to  persist  parallel  with  the  coast  from  which  the 
material  is  derived,  and  in  any  deep-sea  deposits  where  the  con- 
ditions of  supply  are  alike. 

Intergradation  of  beds  of  different  materials. 

EVIDENCES  OF  THE  SLOW  DEPOSITION  OF  SEDIMENTARY  ROCKS. 

1.  Lamination  of  shales. 

2.  Evidences  of  objects  having  lain  long  uncovered  on  the  sea  bottom. 

3.  Beds  formed  from  microscopic  organic  remains   which  commonly  ac- 

cumulate slowly. 

4.  The  rate  in  observed  cases. 

The  silting  up  of  bays,  etc. 

5.  The  wearing  of  pebbles  of  conglomerate  requires  time. 

Great  thickness  of  some  conglomerate  beds. 

6.  Great  conglomerate  beds  made  by  the  passing  of  the  land  through  a 

beach  condition  are  evenly  distributed. 
Example :  Pottsville  conglomerates  of  Pennsylvania. 

7.  The  rate  of  denudation  which  supplies  the  materials  of  mechanical 

sediments. 

The  thickness  of  beds  suggests,  but  does  not  show  positively,  the  length  of 
time  they  were  forming. 

HARDENING  OF  ROCKS. 

The  hardening  of  rocks  may  be  produced  either  chemically  or  mechani- 
cally, or  by  some  combination  of  both  methods. 
Chemically. 

1.  By  the  deposition  of  lime  carbonate,  silica,  iron,  or  other  mineral. 

2.  By  the  elevation  of  temperature  in  the  presence  of  water. 
Mechanically. 

3.  By  pressure. 
Hardening  is  now  going  on.t 

1.  Bog-iron  and  maganese  deposits. 

2.  Hardening  of  road-metal  with  iron. 

*  Footprints  in  the  rocks.    By  C.  H.  Hitchcock.    Pop.  Sci.  Mo.,  Aug.  1873,  pp  428-441 
t  Woodward's  Geology  of  England  and  Wales.    3d  ed.    546-550,    London,  1887. 


219 


220 


SEDIMENTARY    ROCKS. 


3.  Stone  reefs  of  Pernambuco,  Brazil,  and  western  Palestine.  (See  p.  70.) 

Coquina  of  the  coast  of  Florida. 
^Eolian  sandstone  of  Bermuda. 
Glacial  gravels  locally. 
Spring  deposits  cementing  gravels. 

4.  Hardening  of  building-stone  after  quarrying. 

5.  Experimental  determination  by  Adams  and  Nicolson.* 
The  laws  of  matter  show  that  — 

1.  Stratified  rocks   must  have  accumulated   by  means  of   the  same 

agencies,  and  under  the  same  conditions,  that  govern  the  deposi- 
tion of  similar  materials  at  the  present  time. 

2.  The  oldest  beds  must  have  been  laid  down  first,  and  the  newer  ones 

next  on  top,  and  so  on. 

3.  The  stratified  rocks  were  laid  down  as  soft  sediment  in  an  approxi- 

mately horizontal  position,  and  all  changes  in  them,  whether  by 
consolidation,  folding,  faulting,  or  otherwise,  have  taken  place 
subsequently,  and  are,  in  a  sense,  accidental. 


UNSTRATIFIED,  OR  ERUPTIVE  ROCKS. 

Distinctions  between  sedimentary  and  igneous  rocks. 


IGNEOUS, 
OR  UNSTRATIFIED  ROCKS. 

Crystalline  from  fused  state. 

Massive;  different  flows  may  have 
bedded  appearance. 

No  fossils  except  in  inclusions  and  in 
tuffs. 

Flow  structure. 

Gas  cavities. 

Texture  varies  according  to  condi- 
tions of  cooling.  Under  pressure 
are  coarsely  crystalline.  Without 
pressure,  or  quickly  cooled,  are 
more  glassy. t 

*  Science,  Jan.  21,  1898,  new  ser.,  VII,  82-83.  —  Bui.  Geol.  Soc.  Am.,  1898,  IX. 

t  Size  of  grain  in  igneous  rocks  in  relation  to  the  distance  from  the  cooling  wall.    By 

A.  L.  Queneau.    School  of  Mines  Quar.,  Jan.  1902,  XXIII,  181-195. 
Variation  of  texture,  etc.     By  J.  E.  Spurr.    Jour.  Geol.,  Nov.  1901,  IX,  586-606. 
Causes  of  variation,  eto.    By  T.  L.  Walker.     Am.  Jour.  Sci.,  Nov.  1898,  OLVI,  410-415. 
Plutonic  rocks  of  Garabal  Hill,  etc.      By  Teall  and  Dakyns.     Quar.  Jour.  Geol.  Soc., 

Home.    Nature,  Sept.  19,  1901. 


SEDIMENTARY, 
OR  STRATIFIED  ROCKS. 

Clastic,  or  of  fragments 

Bedded 

Contain  fossils 

No  flow  structure 

No  gas  cavities 

Texture  varies  according  to  currents 
in  which  deposited. 


221 


222 


IGNEOUS    ROCKS. 


GROUPING  OF  IGNEOUS  ROCKS. 


'With  reference  j 
to  conditions  of  { 
cooling. 


Those  cooling  under  pressure  at 
great  depths.  They  are,  or  have 
been,  deep-seated,  and  have  been 
exposed  here  and  there  by  eros- 
ion. 


Igneous  rocks 
may  be 
grouped 


With    reference 
to  composition. 


'  Volcanic. 

/Acid,  containing  60  to  75%  of  silica.]  Granites. 

They  are  light  colored.  1  Gneisses. 

Fuse  with  difficulty. 

Stiffen  readily,  and  form  glasses. 

Basic,  containing  less  than  60%  of  silica,  and 
high  percentages  of  fluxes,  lime,  soda,  pot- 
ash, iron,  etc.  They  are  dark  colored,  and 

1.  Easily  fusible  (basalts). 

2.  Medium  fusibility  (andesites). 

3.  Difficult  to  fuse  (trachites). 


FOKMS  OF  IGNEOUS  DEPOSITS. 

Ejected  as  local  lava  flows  of  fragmental  material,  they  form  — 

1.  Lava  cones;  angle  varies  with  fluidity,  3°  to  25°. 

2.  Cinder  cones,  35°  to  40°. 

Craters  are  the  cup-shaped  mouths  of  volcanoes. 

Origin  of  the  cup  shape.* 
Lava  sheets  often  spread  over  wide  areas. 
Overwhelm  topography. 

Deccan  trap  of  India  covers  200,000  square  miles,  100  to  6,000  feet  thick. 
Oregon,  Washington,  and  California,  150,000  square  miles. 
Lava  surfaces  are  usually  very  rough. 
Origin  of  the  Table  Mountains  of  California. 
Often  called  trap,  from  the  Swedish  trappa,  stairs. 
The  lava-capped  hills  of  western  Arizona. 
Columns  may  be  horizontal  and  in  piles. 

Examples:  Fingal's  Cave,  Scotland ;  Giant's  Causeway,  Ireland. 

They  may  curve.t    (See  Plate  XVII.) 
Intrusions. 

Between  beds. 

Vertical. 

Horizontal. 

*  The  moon's  face.    By  G.  K.  Gilbert.    Phil.  Soc.  of  Wash.,  1892,  Bui.,  vol.  XII,  241-292.- 

Lassen  Peak  folio,  U.  S.  Geol.  Surv.    By  J.  S.  Diller.    Washington,  1895. 
t  Iddings.      Am.  Jour.  Sci.,  1886,  CXXXI,  321-324. 
Humboldt.    Atlas  Pittoresque,  123-124.    Paris,  1810. 


223 


224 


IGNEOUS    ROCKS. 


Fig.  49.— Horizontal  columns  of  basalt  exposed  on  the  shores  of  Fernando  de  Xoronha. 

Laccolites.     (See  page  154.) 

Across  beds. 
Dikes. 

Irregularities  of  dikes.     (See  page  152.) 
Tuffs. 

Fragmentary  materials ;  take  the  slope  of  loose  sands  or  cinders. 

Sometimes  deposited  in  water;  may  have  fossils. 

Gross  forms  of  tuffs  are  like  those  of  sedimentary  rocks,  but  they  are 
limited  in  extent  to  the  vicinity  of  the  volcanoes  from  which 
they  are  derived. 


Mineral  Veins. 

Mineral  veins  are  of  small  extent,  but  of  great  economic  importance. 
Minerals  of  economic  importance,  however,  do  not  always  occur  in  veins. 


225 


226  MINERAL   VEINS. 

The  position  of  mineral  veins  among  economic  geologic  deposits  will  be 
understood  from  the  following : 

(  1.  Organic  accumulations:  coal,  lignite,  limestone,  chalk,  phos- 
phates. 

2.  Mechanical  accumulations:  placer  gold,  diamonds,  tin,  mag- 
.bconomic  .    .  , 

.      ,  netic  iron  sands. 

"\  3.  Igneous,  or  metamorphosed  deposits:  certain  building-stones, 
slates,  some  iron  ores. 

4.  Bedded  chemical  deposits:  salt,  gypsum. 

5.  Vein  deposits  or  lodes. 

Veins  are  sheets  of  rocks  filling  fissures  in  other  rocks.* 
Difference  between  veins  and  dikes. 

Dikes  are  crevices  in  the  rock  filled  with  molten  rocks. 

Dikes  of  sandstone  exceptional.    (See  page  238.) 

Veins  are  crevices  filled  with  mineral  deposited  from  solution  in  under- 
ground waters. t 
False  veins  are  crevices  filled  from  above  or  below.     (See  Sandstone 

dikes,  p.  238.) 

If  veins  are  made  by  minerals  filling  crevices  and   cracks  in  the  rocks, 
it  becomes  important  to  understand  the  forms,  sizes,  and   depths 
of  cavities  in  the  rocks. 
Origin  of  crevices. 

1.  By  torsion,  or  twisting  of  the  rocks. t 

2.  Earthquake  jars  when  the  rocks  are  under  tension. 

3.  Faults. 

4.  Openings  along  the  crests  of  anticlines  and  the  bottoms  of  synclines 

when  the  beds  are  folded. 

5.  Shrinkage  due  to  dolomitization  and  loss  of  water. 

Shrinkage  cracks,  however,  are  irregular  and  meandering. 

6.  Pressure  in  any  direction  exceeding  the  crushing  strength  of  the 

rocks. 
Such  pressure  is  often  accompanied  by  faults,  but  such  faults  are 

frequently  so  small  as  to  be  almost  imperceptible. 
Enlargement  of  fractures. 

What  were  originally  mere  cracks  sometimes  becomes  greatly  enlarged. 
This  enlargement  may  be  produced  by  — 

1.  The  expansion  due  to  crystallization  of  minerals  in  the  incipient 

crevice. 
Example:  geodes. 

2.  The  solution  and  removal  of  the  rock  walls. 

Example :  the  brecciated  beds  and  deposits  of  the  Ozarks. 

*  Mining  geology  of  the  Cripple  Creek  district,  Colorado.    By  R.  A.  F.  Penrose,  Jr.    16th 

ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  144-150.    Washington,  1895. 
t  The  movements  of  underground  waters  of  Craven.     Geol.  Mag.,  Feb.  1901,  VIII,  72-75; 

Feb.  1901,  VIII,  75-77. 
|  Daubree,  Geologic  experimentale,  307-314.    Paris,  1879. 


227 


228 


MINERAL    VEINS. 


Fig.  50.— Geodes  formed  in  the  stem  of  a  crinoid.     The  deposition  of  quartz  began  in  the 
hollow  stem  which  was  finally  broken  asunder.    Natural  size. 

Depth  of  crevices. 

Rocks  closely  confined  flow  under  great  pressure. 

At  certain  depths,  about  six  miles,  crevices  can  not  remain  open.* 

Experiments  of  Adams  and  Nicolson.t 
Veins  formed  in  open  crevices  must  have  formed  within  the  zone  of 

rock  stability. 
Thickness  of  veins. 

Varies  from  a  fraction  of  an  inch  to  many  feet. 
Forms  of  veins. t 

May  be  single  or  in  sets,  and  parallel. § 
Some  veins  anastamose  is  all  directions. 
Vary  in  size  in  different  parts  of  the  same  vein. 
Materials  of  veins. 

Various  minerals  carried  in  and  deposited  from  solution. 
Banded. 
Brecciated. 

*  Flow  and  fracture  of  rocks.    By  L.  M.  Hoskins.    16th  ann.  rep.  U.  S.  Geol.  Surv.,  845- 

,  874.     Washington,  1896. 
Metamorphism  of  rocks  and  rock  flowage.     By  C.  R.  Van  Hise.     Am.  Jour.   Sci.,  July 

1898,  CLVI,  75-91.  —  Bui.  Geol.  Soc.  Am.,  1898,  IX,  269-328. 
t  Science,  Jan.  21,  1898,  VII,  82^;  Jan.  18,  1901,  XIII,  95-97. 
An   experimental  investigation  into  the  flow  of  marble.     By  F.  D.  Adams  and  J.  J. 

Nicolson.    Phil.  Trans.  Roy.  Soc.,  London,  1901,  vol.  CXCV,  363-401. 
Ueber  die  Plasticitiit  der  Gesteine.    Von  E.  Weinschenk.     Centralblatt  f.  Min.  Geol.  u. 

Pal.,  1902,  pp.  161-171. 
t  The  gold  quartz  veins  of  Nevada  City  and  Grass  Valley  districts,  California.     By  W. 

Lindgren.    17th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  158-170.    Washington,  1897. 
?  Quar.  Jour.  Geol.  Soc.,  L,  plate  27,  p.  658.    London,  1894. 


229 


230 


MINERAL    VEINS. 


Occurrence  of  veins. 

Veins  are  more  abundant  in  metamorphosed  rocks,  and  in  some  moun- 
tain regions,  because  these  are  often  the  seats  of  dynamic  action 
and  the  rearrangement  of  minerals. 
Mineralizing  agencies  often  more  active  in  such  regions. 
The  filling  of  veins. 

Theories  concerning  the  source  of  the  vein  materials.* 

1.  From  below  (Posepny,  Newberry,  and  others). 

2.  From  above  (Werner  and  Wallace). 

3.  From  sides,  or  lateral  secretions!  (Sandberger,}  Win  slow,  Van 

Hise). 
Processes  of  filling. 

1.  From  volatilization,  i.  e.,  from  gases  or  fumes. 

Example:  sulphur. 

2.  From  hot  waters  holding  minerals  in  solution. 

Examples:  box-pipe  from  Comstock  lode ;  hot  springs  deposits. 

3.  From  deposits   by  waters  containing  mineral   in   solution   at 

ordinary  temperatures. 
How  minerals  change  in  depth.§ 
Oxides  and  free  gold  above. 
Sul pli ides  below.  * 


Fig.  51. — Section  of  a  box-pipe  used  for  ten  years  in  the  Comstock  mines  to  carry  mine 

water  from  one  level  to  another.    The  box  is  lined  with  aragonite  more 

than  half  an  inch  thick,  deposited  by  the  water. 

*  Kemp's  Ore  deposits,  42-55.    New  York,  1893. 
t  Trans.  Am.  Inst.  Min.  Eng.,  1893,  XXII,  634,  735. 
Winslow.    Jour.  Geol.,  1894,  I,  617. 

Posepny's  Genesis  of  ore  deposits.    174-176.    New  York,  1895. 
Branner.    Zinc  and  lead  deposits  of  Arkansas.   15-24. 
t  Canadian  Naturalist,  new  ser.,  1877,  VIII,  345-362. 

\  The  superficial  alteration  of  ore  deposits.     By  R.  A.  F.  Penrose,  Jr.    Jour.  Geol.,  1894, 
II,  288-317. 


231 


232 


MINERAL   VEINS. 


Uncertainties  in  mining  for  precious  metals,  in  so  far  as  they  depend  upon 
the  extent  of  the  ore  deposits,  are  due  to  — 

1.  Irregularity  of  veins,  fractures,  or  crevices  in  which  the  ores  exist. 

2.  Irregularity  of  the  conditions  of  deposition. 

3.  Irregularities  due  to  displacements  since  deposition. 
The  risks  of  mining  are  due  largely  to  these  uncertainties. 

If  rocks  were  uniform  in  texture  and  composition,  and  if  we  knew  the 
conditions  and  stresses  under  which  they  have  been  formed,  the 
positions  of  the  veins  might  be  calculated. 
Certainty  of  mining  bedded  deposits. 

Coal,  lignite,  and  gypsum;  salt,  asphaltum,  etc. 

South  African  gold  beds.* 


Fig.  52.— Bedded  ore  deposits  (black)  interstratifled  with  other  horizontal  rocks. 


Fig.  53.— Section  of  the  Glencairn  property  in  the  Rand,  showing  portions  of  four  reefs 
or  bedded  ore  deposits.    (Hatch  and  Chalmers.) 


Fig.  54.— Section  through  shafts  in  the  Rand  gold  field,  showing  the  regularity  of  the 
structure.    (Hatch  and  Chalmers.) 


*  Gold  mines  of  the  Rand.    By  F.  H.  Hatch  and  J.  A.  Chalmers.     London,  1895. 
Les  mines  d'or  du  Transvaal.    Par  L.  de  Launay.    Paris,  1896. 


233 


234  JOINTS    IN    ROCKS. 

Terms  used. 

Lode;  mother  lode. 

Foot- wall. 

Hanging-wall. 

Country  rock. 

Gangue  (quartz  common). 

Horse. 
Placer  deposits. 

Origin  of  the  gold  in  placer  deposits. 

How  the  original  quartz  veins  were  discovered. 

How  rich  placers  may  be  derived  from  poor  vein  deposits. 

Diamond  placers  of  Brazil ;  tin  placers  of  the  Malay  peninsula. 


STRUCTURAL  FEATURES  COMMON  IN  ROCKS. 

Joints  in  Rocks.* 

Joints  are  fractures,  or  clean-cut  faces,  that  pass  through  rocks  regardless 

of  the  bedding  planes. 
All  rocks  have  more  or  less  of  them. 
They  are  common  in  shales ;  "  block  coal  "  of  Indiana. 
Exposed  and  used  in  quarries. 
Pass  through  pebbles. 

They  may  lie  in  two  or  more  directions;  they  frequently  occur  in  sets. 
Joints  often  influence  topography. t 

Cliffs  of  Cayuga  lake;  in  loess ;{  with  veins  in  them.     (See  Plate 

XVIII.) 

Joints  are  not  confined  to  hard  rocks,  but  occur  in  sands  §  and  clays. 
Joints  of  basaltic  columns. 

Horizontal  sheets  of  lava  are  sometimes  vertically  jointed  so  as  to 

form  hexagonal  columns. 

Why  the  columns  are  approximately  hexagonal. || 
A  plane  surface  can  be  covered  by  only  three  regular  figures : 
square,  equilateral  triangle,  and  hexagon.    These  form  about 
a  point  the  respective  angles :  90°,  60°,  and  120°. 

*  Daubrge.    Geologic  experimentaie.    300-318.    Paris,  1879. 

On  the  fracture  system  of  joints.  By  J.  B.  Woodworth.  Proc.  Boston  Soc.  Nat.  Hist., 
1896,  XXVII,  163-183. 

Crosby.  Proc.  Boston  Soc.  Nat.  Hist.,  XXII^  72-85.  Boston,  1884.  —XXIII,  243-248,  Bos- 
ton, 1888. 

t  Button's  High  plateaus  of  Utah.    280.    Washington,  1880. 

Erosion  forms  in  Harney  Peak  district,  South  Dakota.  By  E.  O.  Hovey.  Bui.  Geol. 
Soc.  Am.,  XI,  581-582,  plates. 

t  Ann.  rep.  Geol.  Surv.  Iowa,  VII,  235.    Des  Moines,  1897. 

2  Freeland.    Trans.  Am.  Inst.  Min.  Eng.,  XXI,  491. 

\  J.  Lomas.    Proc.  Liverpool  Geol.  Soc.,  1895,  VII,  pt.  3,  pp.  323-325. 

Open-air  studies.     By  G.  A.  J.  Cole.     Plates  VI  and  VIII,  opp.  pp.  172  and  183.    London, 


"S  ® 

13    *1 


235 


236 


JOINTS    IN    ROCKS. 


Fig.  55.— Jointed  shales  on  the  east  shore  of  Cayuga  Lake,  N.  Y.    (Martin.) 


Fig.  56. — A  vertical  dike  of  sandstone  cutting  inclined  beds  of  diatomaceous  shales, 
Graves  creek,  San  Luis  Obispo  county,  Gal.    (Newsom.) 


237 


238 


JOINTS    IN    ROCKS. 


Sandstone  dikes.* 

Joints  or  cracks  in  the  rocks  are  occasionally  filled  with  what  are  called 

sandstone  dikes. 
These  are  usually  carried  by  water,  or  some  other  fluid,  from  soft 

sands  into  open  crevices. 

Sandstone  dikes  are  common  near  Santa  Cruz,  and  on  Graves 
creek,  San  Luis  Obispo  county,   California.     (Plates  XIX 
and  XX.) 
Theories  of  the  causes  of  joints  (other  than  those  of  basaltic  columns). 

1.  Contraction,  as  sun-cracks  in  mud. 

These  are  not  straight  and  clean-cut. 

2.  Torsion. 

DaubreVs  experiments  with  ice.t 

3.  Earthquakes. 

Effect  of  sharp  snaps  on  rocks  under  strain. 

4.  Pressure. 


Fig.  57.  -Fractures  in  blades  of  ice  produced  by  torsion. 


*  Sandstone  dikes.    By  J.  S.  Oilier.    Bui.  Geol.  Soc.  Am  ,  1889.  I,  411-442. 

Intrusive  sandstone  dikes  in  granite.      By  W.  Cross.       Bui.  Geol.  Soc.  Am.,  189-4,  V,  225- 

Dikes  of  Oligocene  sandstone  ...  in  Russia. 

Ill,  49-53.  —  R.  Hay.    Bui.  Geol.  Soc.  Am. 

Sandstone  pipes,  etc.  By  E.  Greenly.  Geol.  Mag.,  Jan.  1900,  pp.  20-24. 
Ransome.  Trans.  Am.  Inst.  Min.  Eng.,  XXX,  227-236.  New  York,  1900. 
t  Geologic  experimentale.  Par  A.  Daubrge.  300-314.  Paris,  1879. 


By  A.  P.  Pavlow.      Geol.  Mag.,  Feb.  1896. 
,  Ill, 


Plate  XX.  —  A  sandstone  dike  cutting  Miocene  diatomaceous  shales,  on  the  beach 

six  miles  west  of  Santa  Cruz,  California.    In  the  foreground  the  dike  material 

has  been  removed  from  the  cavity  by  the  waves.    (Newsom.) 


239 


240  CLEAVAGE    OF    ROCKS. 


The  Cleavage  of  Rocks.* 

Cleavage  is  the  easy  splitting  of  rocks  in  parallel  planes. 
Kinds  of  cleavage  peculiar  to  rocks. 

1.  Crystalline  cleavage. 

Examples:  gypsum,  mica. 
Confined  to  crystalline  forms. 

2.  Bedding  is  due  to  water  sorting,  and  follows  bedding  planes ;  some- 

times called  "  flagstone  cleavage." 

3.  Slaty  cleavage. 

General  facts  regarding  slaty  cleavage. 

1.  It  is  always  associated  with  folded  and  contorted  beds. 

2.  It  cuts  across  the  bedding  planes  at  various  angles. 

3.  It  occurs  only  in  fine-grained  rocks. 

4.  The  included  particles  are  parallel  to  the  cleavage  planes. 
Experiments  show  that  — 

1.  Iron  cooling  without  pressure  is  granular;  when  drawn  like  wire  it 

is  fibrous;  when  rolled  it  has  cleavage  structure,  or  is  scaly;  that 
is,  the  granules  are  flattened. 

2.  Parallel  re-arrangement  of  mica  scales  in  clay  after  pressure. 

3.  Pressure  on  beeswax  causes  it, to  separate  into  folia,  or  scales. 
These  facts  all  suggest  that  slaty  cleavage  is  caused  by  pressure  at  right  angles 

to  the  cleavage  planes. 
This  is  borne  out  — 

1.  By  finding  wrinkled  sand-beds  in  slates. 

2.  By  the  general  folding  of  the  rocks  of  slate  regions. 

3.  By  the  deformation  of  fossils  in  the  slates. 

4.  By  the  minerals  in  the  slates  all  lying  parallel  to  the  cleavage. 
It  is  also  thought  that  pressure  alone  is  not  capable  of  producing  slaty 

cleavage,  but  that  chemical  action  accompanies  it.t 

SCHISTOSITY. 

Schistosity  is  a  parallel  splitting  of  the  rock  in  thin  layers,  but,  unlike 

slaty  cleavage,  the  layers  are  more  or  less  wrinkled. 
The  rocks  often  have  a  felted  appearance. 
Schistosity  is  supposed  to  be  due  to  squeezing  or  shearing }  at  depth. 

*  On  cleavage,  joints  and  folds,  see  Dale  in  16th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  I,  549- 
570. 

Cleavage  and  flssility.  By  C.  R.  Van  Hise.  16th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  I,  633. 
(Bibliography.)  Washington,  1896. 

Deformation  of  rocks.    By  C.  R.  Van  Hise.    Jour.  Geol.,  1895,  IV,  449-483,  593-629. 

On  slaty  cleavage  and  allied  rock  structure,  etc.  By  Alfred  Barker.  Rep.  Brit.  Assn., 
1885,  pp.  813,  852.  (Many  references.) 

t  The  phyllades  of  the  Ardennes  compared  with  the  slates  of  North  Wales.  By  T.  Mel- 
lard  Reade  and  Philip  Holland.  Proc.  Liverpool  Geol.  Soc.,  1899-1900,  pp.  463-478. 

Reade.    Proc.  Liverpool  Geol.  Soc.,  1900-1901,  pp.  101-128. 

t  Hoskins.    16th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  I,  870.    Washington,  1896. 


241 


242 


CONCRETIONS. 


Concretions.* 

Concretions  commonly  occur  as  round  or  lenticular  masses  of  various  sizes, 

from  that  of  a  pin-head  to  several  feet  in  diameter.     (Plate  XXI.) 
How  they  differ  from  pebbles  and  boulders. 

Due  to  the  tendency  of  certain  minerals  in  solution,  or  fusion,  to  segre- 
gate as  they  are  deposited  or  crystallized. 
They  may  occur  in  either  igneous  or  sedimentary  rocks. 

1.  Contemporaneous  with,  or  part  of,  enclosing  beds. 

Rogenstein,  bauxite. 

2.  Formed  subsequently. 

Bedding  planes  sometimes  pass  through  concretions. 

Commonly  formed  along  certain  beds. 

Concretions  in  sandstone  are  apt  to  be  of  lime ;  those  in  limestone  are 
apt  to  be  of  silica. 

Liable  to  form  about  bones  or  shells. 

Loess-puppets,  fantastic  forms,  of  lime  concretions  in  the  loess. 
Geodes,  or  hollow  concretions. 

Geode  beds  of  Warsaw,  Illinois;  Keokuk,  Iowa;  Indiana,  etc. 

Geodes  may  be  empty  or  filled  with  calcite,  dolomite,  gypsum,  chal- 
cedony, quartz,  zinc  blende,  pitch,  petroleum. 

Formed  after  the  deposition  of  the  beds. 

The  "  iron  pots,"  or  iron  geodes,  of  Arkansas. t 


Fig.  58.—  Concretions  of  iron  and  clay  from  the  Tertiary  beds  of  South  Arkansas. 
(Harris.) 


*  Merrill.    Proc.  U.  S.  Nat.  Mus.,  XVII,  87-88,  and  plate.    Washington,  1895. 

John  Ruskin     Geol.  Mag.,  1867,  pp.  338,  481;  1868,  pp.  12,  156.  208;  1869,  p.  529. 

T.  S.  Hunt.    Canadian  Nat.,  1881,  IX,  431-433 

Gratacap.    Am.  Nat.,  1884,  XVIII,  882-892. 

Bell.    Am.  Jour.  Sci.,  Apr.  1901,  XI,  315-316. 

Concretions  from  the  Champlain  clays   of   the  Connecticut  Valley.     By  J.  M.  Anns 

Sheldon.    With  160  illustrations.    Boston,  1900. 
Stocks.    Geol.  Mag.,  Jan.  1902,  IX,  44-45.  —  Stocks.    Quar.  Jour.  Geol.  Soc..  LVIII,  46-58. 

London,  1902. 
t  On  the  ...  siliceous  nodular  brown  hematite  (Gothite)   in  the  Carboniferous  lime- 

stone    .  .  near  Cookstown,  county  Tyrone,  etc.      By  E.  T.  Hardman.    Jour.  Roy. 

Geol.  Soc.,  Ireland,  II,  new  ser.,  1870-73,  pp.  150-158. 


Plate  XXI.  —  A  spherical  calcareous  concretion  from  sandstone. 
Piru,  Ventura  County,  California. 


243 


244 


CONCRETIONS. 


Fig.  59.— Concretions  from  the  Champlain  clays  of  the  Connecticut  Valley;  natural  size. 
(Mrs.  Sheldon.) 


245 


246  CONCRETIONS. 

Oolites  *  and  pisolites  (pea-stones)  are  concretions  of  smaller  size. 

Formation  of  pisolite  at  Carlsbad,  where  it  is  called  rogenstein. 

Siliceous  oolite  from  Pennsylvania. 

Oolitic  limestones  of  Indiana. 
Concretionary  structure  in  crystalline  rocks. 

Due  to  concentric  arrangement  of  the  crystals  in  cooling. 

"  Orbicular  granite."  t 

Note  that  — 

1.  Concentric  staining  is  not  properly  a  concretion.     It  is  caused 

by  penetration  of  mineral-charged  waters,  and  the  oxida- 
tion or  deposition  of  the  minerals. 

2.  Exfoliation,  or  spheroidal  weathering,  produces  rounded  forms 

which  are  not  concretions,  though  resembling  them.; 

STYLOLITES,  OB  CONE-IN-CONE. § 

Stylolite  is  a  columnar,  or  tooth-like  structure,  from  a  fraction  of  an  inch  to 
three  inches  long,  sometimes  found  in  limestones;  it  is  caused  by 
pressure  of  the  overlying  beds. 

FULGURITES.II 

A  fulgurite  is  a  tube  one  or  two  inches  in  diameter  formed  by  lightning 
fusing  soil  or  sand.  It  is  sometimes  formed  in  hard  rock. 

*  Bibliography  of  oolites.    By  T.  C.  Hopkins.    21st  aim.  rep.  Indiana  Geol.  Surv.,  409-410. 

Indianapolis,  1897. 

The  Geologist,  1858,  pp.  73-73.    (Insect  eggs  as  oolites.) 
Nature,  Nov.  12,  1896,  LV,  40.     (Bacterial  origin  of  oolite.) 
E.  B.  Wethered.    Quar.  Jour.  Geol.  Soc.,  1891,  LI,  196.     (Organic  origin.) 
E.  H.  Barbour  and  Jos.  Torrey.    Am.  Jour.  Sci.,  1890,  CXL,  246-249. 

G.  R.  Wieland.     Am.  Jour.  Sci.,  1897,  CLIV,  262-264.      (Pennsylvania  siliceous  oolites.) 
Rothpletz.    Am.  Geol.,  1892,  X,  278-282. 
Griswold  and  Agassiz.   Bui.  Mus.  Comp.  Zool.,  vol.  38,  no.  2,  pp.  29-62.    (Florida  oolites.) 

—  Jour.  Geol.,  V,  312-313. 

t  Bulletin  de  la  Commission  Geologique  de  Finland,  no.  4,  plates  1  and  2. 
Concretions  in  Canadian  rocks.     By  T.  C.  Weston.     Trans.  Nova  Scotia  Sci.,  1894-95, 

The  hollow  spherulites  of  the  Yellowstone  and  Great  Britain.    By  John  Parkinson. 

Quar.  Jour.  Geol.  Soc.,  May  1901,  LVII,  211-225. 

Geikie's  Ancient  volcanoes  of  Great  Britain.     I,  22.    Illustration.    London,  1897. 
t  On  spheroidal  structure  in  Silurian  rocks.    By  J.  D.  La  Touche.    Jour.  Roy.  Geol.  Soc. 

Ireland,  II,  1867-70,  pp.  229-232.    Edinburg,  1871. 

?  Am.  Jour.  Sci.,  1885,  pp.  130,  78-79.  —  Geol.  Mag.,  Nov.  1892,  IX,  505-507. 
H.  C.  Sorby.    Trans.  Brit.  Assn.,  1859,  p.  124. 
20th  ann.  rep.  Indiana  Geol.  Surv.,  82.    Indianapolis,  1896. 

21st  idem,  305-308;  bibliography.    Indianapolis,  1897.  -  Ind.  rep.  for  1873,  p.  275. 
Gresley.    Quar.  Jour.  Geol.  Soc.,  1894,  L,  731-739,  2  plates. 
Abstract  Am.  Geol.,  1894,  XIV,  399-400.  —  Cole.    Mineralogical  Mag.,  X,  136. 
A.  J.  Sachs.    Proc.  Austr.  Assn.  Adv.  Sci.,  1893,  IV,  327-328. 

I  A  spiral  fulgurite  from  Wisconsin.      By  W.  H.  Hobbs.     Am.  Jour.  Sci.,  CLVIII,  17-20. 
Fulgurites  from  Tupungato  and  the  summit  of  Aconcagua.    By  T.  G.  Bonney.     Geol. 

Mag.,  Jan.  1899,  pp.  1-4. 
A  study  of  the  structure  of  fulgurites.    By  A.  A.  Julien.    Jour.  Geol.,  Dec.  1901,  IX,  673- 

693. 


247 


248 


DISPLACEMENTS    OF    ROCKS. 


Displacements  of  Rocks. 
EVIDENCES  OF  ELEVATION  AND  DEPRESSION.     (Plate  XXII.) 

1.  Evidences  that  most  sedimentary  beds  were  deposited  in  the  ocean. 

a.  They  are  water-bedded. 

b.  They  contain  remains  of  marine  animals. 

2.  As  they  are  now  on  land,  in  hills  and  mountains,  they  must  have  been 

elevated.* 
But  it  has  been  shown  that  while  the  earth's  surface  rises  in  one  place  it  is 

depressed  at  another,  so  that  there  must  be  a  warping  of  the  beds. 
This  may  produce  tilting ,  folding ,  or  faulting. 


,  60.— Section  across  the  saddle- reef  folds  at  Hargreaves,  New  South  Wales,  showing 
the  ores  in  the  anticlines.    (Watt.) 


Theory  of  isostacy. 

Isostacy  refers  to  a  state  of 

equilibrium. 
(This    is  discussed    at 
length  under  Physi- 
ography, Part  IV.) 
Geologic  importance  of  folds  and 

faults. 
Economic  importance. 

Examples :  the  mining 
of    bedded  deposits, 
like  coal  and  iron. 
The  broader  structural  features 
of  the  earth  are  exhibited 
in  folds  and  faults. 
Means  of  studying  rock  beds. 
1.    Artificial    sections    are 
exposed     in    mines, 
shafts,  and  wells. 
These  seldom  penetrate 
more  than  3,000  feet. 
Well  near  Leipzig  6,560 
feet. 


mm^-^ 

Hat 


Fig.  61.— Section  across  a  saddle  reef, Victoria, 

Australia,  showing  the  ore  in  the  crest 

of  the  anticline.     (Rickard.) 


*  Fairbanks.    Am.  Geol.,  Oct.  1897,  XX,  213,  245. 


249 


250 


DISPLACEMENTS    OF    ROCKS. 


\Lower  HeWerbero Limestone 
\Louoe_r<Stfuri<in  Limestone 

Fig.  62.— Section  across  the  Rich  Patch  iron  deposits  of  Virginia,  showing  the  relation  of 
the  ore  to  the  geologic  structure. 


Fig.  63. — Section  through  the  Bendigo  gold  fields  of  Victoria,  Australia,  showing  the 
saddle  reefs  in  anticlines  and  synclines.     (Schmeisser.) 


Fig.  64.— Cross-sections  showing  the  structure  of  the  oil-bearing  strata  of  the  Trans- 
Caucasian  region,  Russia. 


251 


252  DISPLACEMENTS    OF    ROCKS. 

2.  Natural  sections  are  exposed  in  canons. 

Grand  canon  of  the  Colorado  is  over  6,000  feet  deep. 

3.  Natural  sections  are  exposed  in  eroded  folds  and  faults. 

These  bring  the  deep-seated  beds  to  view. 

TILTING. 

Recent  tilting  shown  in  the  Great  Lakes  region  by  level-lines. 

Tilt  to  the  southwest. 

If  tilting  should  continue  at  this  rate  Chicago,  in  500-600  years,  will 
have  occasional  discharge  to  the  Illinois  river;  in  1,500  years  it 
will  be  continuous.  At  the  present  rate,  in  3,000  years  Niagara 
will  cease  to  flow,  and  the  water  of  the  Great  Lakes  will  dis- 
charge toward  the  south.* 

FOLDING,  t 

One  of  the  postulates  of  geology  is  that  — 

1.  Sedimentary  rocks  were  originally  laid  down  in  approximately  hori- 

zontal beds. 
If  this  is  true  it  follows  that  — 

2.  Folds,  tiltings,  and  faults  in  sedimentary  rocks  were  made  subsequently. 
Folds  are  wrinkles  of  various  sizes. 

1.  Broad  and  gentle,  with  axes  far  apart.     (No.  4  in  Fig.  66.) 

2.  Sharply  crumpled. i 

Crumpling  is  very  marked  in  many  schists. 

3.  Overturned.     (Nos.  6  and  11  in  Figs.  66  and  67.) 

4.  Radiate,  or  fan-shaped,  as  in  the  Alps.§ 


Fig.  65.— Illustrations  of  folded  structure.    (Drake.) 

Technical  names  applied  to  parts  of  folds. 

An  outcrop  is  an  exposure  of  rock  in  place  at  the  surface. 
An  axis  is  an  imaginary  plane  along  which  a  fold  occurs. 
Dying  out  and  overlapping  of  axes. 

*  G.  K.  Gilbert.    Nat.  Geog.  Mag.,  Sept.  1897,  VIII,  747. 

Le  nivellement  g6n6rale  de  la  France.    Par  Charles  Lallemand.     Ann.  des  mines,  9me 

se>.,  XVI,  227-306.  -  Bui.  Soc.  Beige  de  Geologic,  1891,  V,  13-20. 
t  The  mechanics  of  Appalachian  structure.     By  Bailey  Willis.     13th  ann.  rep.  U.  S. 

Geol.  Surv.,  pt.  II,  211-282.    Washington,  1893. 

The  folds  of  the  mountains.    Open-air  studies.    By  G.  A.  J.  Cole.  283-313.     London,  1895. 
Deformation  of  rocks.    By  C.  R.  Van  Hise.    Jour.  Geol.,  1896,  IV,  312-353. 
A  fold-making  apparatus,  etc.    Nature,  Aug.  31,  1899,  p.  411. 
t  Geological  structure  ...  of  the  Vermilion  range.     By  H.  L.  Smith  and  J.  R.  Finlay 

Trans.  Am.  Inst.  Min.  Eng.,  XXV,  595-645. 
g  Torsion  structure  in  the  Alps.    Nature,  Sept.  7,  1899,  p.  443. 


253 


254 


DISPLACEMENTS    OF    ROCKS. 


Fig.  66.— Sections  showing  types  of  structure  and  topography  in  the  Paleozoic  region  of 

southwest  Arkansas.    No.  5  is  a  section  across  two  anticlines 

and  one  syncline.    (Ashley.) 


DISPLACEMENTS    OF    ROCKS. 


255 


Fig.  67.— Sections  across  anticlines  showing  types  of  structures  and  topography  in  the 

Paleozoic  region  of  southwest  Arkansas.    The  dotted  areas  represent 

sandstones,  and  the  shaded  parts  shales.     (Ashley.) 


256 


DISPLACEMENTS    OF    ROCKS. 


Anticline. 

Syncline.     (Middle  of  No.  5.  in  Fig.  66.) 

Monocline,  or  a  slope  in  one  direction  (but  not  an  overturn). 

Location  of  axes  by  the  use  of  the  dips,  when  the  exposures  are  many 

or  few. 
Dip  is  the  slope  of  a  bed  of  rock  down  which  water  or  a  ball  would  run. 

Dip  is  measured  by  the  angle  it  makes  with  the  horizon,  and  is 


Clinometer  and  compass. 

Caution  against  false-bedding. 

Caution  against  apparently  horizontal  beds. 

Caution  against  "  creep."  * 

Use  of  dip  in  locating  beds  in  depth. 

Width  of  the  outcrop  varies  with  the  dip. 

Use  of  dip  in  determining  thickness  of  rocks. 
Strike  of  rocks. 

Direction  on  the  surface. 

The  water-line  against  the  face  of  a  bed. 

Use  of  strike  in  tracing  beds  on  the  surface. 
Dying  out  of  folds. 

In  length ;  the  overlapping  of  folds. 

In  depth,  as  shown  in  mines,  where  the  rocks  crush  or  compress  in 

depth,  instead  of  folding. 
The  anticlines  are  elevated  more  than  the  synclines  are  depressed.* 

What  is  meant  by  rocks  being  geologically  higlier. 

Not  a  matter  of  hypsometry. 

How  outcrops  with  various  dips  look  on  geological  maps. 
Meaning  of  colors  on  geological  maps. 
Appearance  of  eynclines ;  of  anticlines. 
How  outcrops  in  folded  areas  follow  the  hills  according  to  dip. 


a 


Fig.  68.—  Diagram  illustrating  the  effect  of  horizontal  pressure  upon  a  horizontal 
homogeneous  bed.    (Ashley.) 


*  For  illustration  of  creep,  see  Scott's  Geology,  82. 
t  Van  Hise.     Jour.  Geol.,  1898,  VI,  19.  —  Buckley.     Tr 


rans.  Wis.  Acad.  Sci.,  XIII,  156. 


257 


258 


A    GEOLOGICAL    MAP. 


A  TYPICAL  EXAMPLE 

OFTHB 

GEOLOGY  OF  NORTH  ARKANSAS 

LOWER  CARBONIFEROUS   I IOHDOVICIAN 

MILE! 


Fig  69.— Type  of  dendritic  exposures  caused  by  the  streams  cutting  through  the  upper 
and  exposing  the  underlying  strata  in  a  region  of  horizontal  beds. 


OVERTURNED    ANTICLINES. 


259 


6  xat/t  j>  3 

Fig.  70.— North-south  sections,  ten  miles  apart,  across  an  anticline  in  the  Coal  Meas- 
ures of  Indian  Territory.    The  section  at  the  topis  farthest  west;  toward 
the  east  the  fold  merges  into  a  fault.     (Drake.) 


Fig.  71. — An  overturned  anticline.    The  resisting  beds  are  sandstones.    (Ashley.) 


260 


STRUCTURE. 


b  //       _    b 

Fig.  72.— Diagrams  showing  the  effect  of  original  dip  upon  ultimate  structure.   (Ashley.) 


Fig.  73.— Profiles  of  an  anticlinal  ridge,  Antoine  mountain,  Pike  county,  Arkansas. 
(Ashley.) 


261 


262 


FAULTS. 


Overturns.* 

Influence  of  original  dip  upon  overturns. 

Overthrust  folds  form  more  readily  than  underthrust  folds,  because 

of  the  easier  relief  being  upward.t 
Effects  of  folds  on  topography. 

1.  Anticlinal  valleys.  4.  Monoclinal  hills. 

2.  Synclinal  valleys.  5.  Anticlinal  hills. 

3.  Synclinal  hills.       ••  Weak  structures. 

Strong  structures.  6.  Isoclinal  ridges. 

FAULTS.* 

Faults  are  displacements  of  the  rocks  along  lines  of  fracture. 
They  are  of  much  more  importance  in  economic  geology,  partly  because 
ore  deposits  are  often  formed  along  faults,  and  partly  because  they 
frequently  displace  ore  bodies  after  they  have  been  deposited. 
Faults  may  run  in  any  direction. 

They  can  only  take  place  after  the  formation  of  the  beds  so  faulted. 
They  occur  singly  or  in  sets. 

These  sets  may  cross  each  other  at  various  angles. 

Faults  are  called  normal,  or  reversed,  according  to  the  nature  of  the  dis- 
placement. 

NORMAL  OR  GRAVITY  FAULTS. § 

Produced  by  tension  of  the  beds,  allowing  one  side  to  settle. 

"Faults  hade  to  the  downthrow,"  a  rule  originating  in  a  region  of 
normal     or     gravity 
faults,  and  of  approx- 
imately     horizontal 
beds. 

Meaning  of  this  expres- 
sion. 

Gravity  faults  occur  in  regions 
of  surface  contraction,  or 
of  vertical  pressure ;  they 
sometimes  occur  in  soft 
materials.|| 
Contraction  may  be  due  to 


Fig.  74. — Section  across  normal  faults  showing 

the  repetition  of  the  same  beds  at 

different  elevations. 


1.  Drying,    or    loss   of 
water. 

2.  Cooling  of  hot  rocks. 


Fig.  75.— Section  across  normal  faults. 


*  16th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  I,  550.    Washington,  1896. 

t  Van  Hise.     16th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  I,  621.    Washington,  1896. 

Buckley.    Wis.  Acad.  Sci.,  XIII,  159. 

I  Fault-rules.     By  F.  T.  Freeland.      Trans.  Am.  Inst.  Min.  Eng.,  XXI,  491-502.      New 

York,  1892-93.    Contains  short  bibliography. 

La  face  de  la  terre.    Par  E.  Suess.    Tome  I,  138-184.    Paris,  1897. 
Heim  and  De  Margerie.    Dislocations.    Zurich,  1888.     (Bibliography.) 
Slickensides  and  normal  faults.   By  T.  Mellard  Reade.    Proc.  Liverpool  Geol.  Soc.,  1889, 

VI,  92-114. 
I  On  the  origin  of  normal  faults,  etc.     By  Joseph  Le  Conte.     Am.  Jour.  Sci.,  Oct.  1889, 


pp.  257-263. 
aGe 


||  Iowa  Geol.  Surv.  Rep.,  1889,  X,  365-368. 
Freeland.    Trans.  Am.  Inst.  Min.  Eng.,  XXI,  491. 


263 


264 


FAULTS. 


Oregon  lakes,*  Dead  Sea,  and  the  Jordan.t 
California  valleys,  but  widened  by  erosion. 
Deceptive  thickness. 


REVERSED  OR  THRUST  FAULTS.* 


Importance  of  this  rule 


Thrust  faults  are  caused  by  pressure. 
Rule  regarding  the  dip  of  the  fault  is  reversed. 
in  the  location  of  veins  and 
beds. 

Folds  often  merge  into  faults. 
Sled-like    turned  up  ends  of 

beds  on  faults  Fi£-  76.—  Both  depression  and  elevation  of 

fault  blocks  produced  by  pressure  and 
faults  dipping  in  different  directions. 


Fig.  77. — Section  across  folds  that  become  faults  repeating  the  same  beds  along  their 
outcrops.    (Heim  and  de  Margerie.) 


Fig.  78.— A  thrust  fault  displacing  a  quartz  vein.    In  this  case  the  fault  dips  toward 
the  downthrow. 


Topographic  features  due  to  landslides.     By  I.  C.  Russell.     Pop.  Sci.  Mo.,  Aug.  1898. 

•th  America.    By  I.  C.  Russell.    29-31.    Boston,  18 

London,  1886. 


Lakes  of  North  America.    By  I.  C.  Russell.    29-31.    Boston,  1895. 
t  See  maps  in  the  survey  of  Western  Pal 


stine.    By  E.  Hull 
t  Ashley.    Bui.  Geol.  Soc.  Am.,  1897,  IX,  429-431. 


265 


Fig.  79.— An  artificial  fold  passing  into  one  large  and  many  small  faults.    (Willis.) 

Amount  of  displacement  in  faults. 

From  the  fraction  of  an  inch  to  thousands  of  feet. 

Faulted  pebbles. 
15,000  feet  in  Sierras. 
20,000  feet  in  Appalachians. 
40,000  feet  in  Wasatch  Mountains,  Utah. 
Overthrust  faults  of  Scotland. 
Continuity  of  displacements. 
Faults  die  out  below. 
Die  out  longitudinally. 

They  vary  in  length  from  a  few  feet  to  hundreds  of  miles;  one 

in  Africa  is  120  miles  long,*  another  is  270  miles  long. 
There  are  many  long  faults  in  California.     Owens  Lake  fault  150 
miles;  Salinas  valley  fault  about  120  miles;    Santa  Clara 
valley  fault  more  than  200  miles. 

A  shear  fault  has  varying  displacements  at  different  parts  of  the  fault. 
Direction  of  displacement  is  not  necessarily  vertical,  but  may  be 
lateral,  or  side  thrust ;  or  it  may  be  twisted,  one  side  moving 
one  way,  the  other  the  other,  forming  a  double  shear  fault. 
How  vertical  displacement  of  tilted  beds  may  give  the  appearance  of  a 
lateral  displacement. 

*  Nature,  Apr.  22,  1897,  LV,  581. 


267 


268  FAULTS. 


I 


North 


S^cale    of  feet  %-'"'  ''W 


\ 


Fig.  80.— Plan  of  a  laterally  faulted  calcareous  stratum,  San  Lorenzo  river,  Ben  Lo- 
mond, California.    (Newsom.) 

Ages  of  faults. 

A  fault  must  be  newer  than  the  rocks  affected  by  it. 

If  Cambrian  and  Carboniferous  rocks  are  faulted,  the  fault  must  be 

post-Carbonif  erou  s . 

Faults  in  Nova  Scotia  since  the  glacial  epoch.* 
At  some  places  faults  are  now  forming.f 

Edges  of  faults  are  not  straight,  but  ragged  and  more  or  less  crooked. 
Slickensides  are  striae,  or  scratches,  on  the  rocks  between  faces  that 

have  slipped  over  each  other. 
Slickensides  resemble  glacial  striae. 

DETECTION  OF  FAULTS  ON  THE  SURFACE. 

1.  By  the  abrupt  termination  of  beds  along  a  strike. 

Examples:  map  of  France;  Pennsylvania  county  maps. 

2.  By  newer  rocks  apparently  dipping  beneath  older  ones. 

Rush  creek  fault. 

3.  By  mineralization  on  fault-line. 

*  G.  F.  Matthew.    Bui.  XIII,  Nat.  Hist.  Soc.  of  New  Brunswick,  Nov.  1894,  pp.  34-42- 
t  Spurr.    Monograph  XXXI,  U.  S.  Geol.  Surv.,  148-150.    Washington,  1898. 


269 


270 


FAULTS. 


4.  By  certain  springs  emerging  on  the  fault-line.     (See  no.  2.) 

5.  By  changes  of  topography. 

6.  By  change  of  rock  or  soil  on  the  strike  of  the  fault. 

ECONOMIC  IMPORTANCE  OF  FAULTS. 

Mineral  veins  are  often  formed  in  or  near  fault-lines. 
Mineral  deposits  are  displaced  by  .faults. 

It  is  therefore  frequently  important  to  determine  both  the  direction 
and  amount  of  displacement  by  a  fault. 


Fig.  81.— A  normal  fault  in  the  Ozark  Mountains  displacing  beds  of  zinc  ore. 


Fig.  82.— Section  across  two  faulted  reefs  of  the  Rand.    (Hatch  and  Chalmers.) 


Plate  XXIII.  —  A  ledge  of  siliceous  mineralized  rock  along  a  fault-line 
in  the  Ozark  zinc  regions. 


271 


V£   LIMESTONE  tv.Hj  COAHSE  SANDSTONE  J  FINE  GRAINED  SANDSTONE 

OCUABTZ  <•§  RHODOCH80SITE        S)  ORE          1®  SELVAGE 

ENTERPRISE   MINE,  COLORADO. 
Fig.  83.— Ore  deposited  in  a  fault,  Enterprise  mine,  Colorado.    (Rickard. 


272  METAMORPHISM. 


The  Alteration  of  Rocks. 

Rocks  do  not  remain  the  same,  but  are  subject  to  changes. 
Metamorphism  is  one  of  these  changes. 

METAMORPHISM.* 

The  change,  whether  chemical,  mineralogical,  or  other  rearrangement, 

that  rocks  undergo  after  their  original  formation  or  deposition. 
It  often  obscures  the  — 

1.  Original  form. 

2.  Method  of  formation. 

Not  all  changes  are  spoken  of  as  metamorphism,  though  the  distinction  is 
sometimes  quite  arbitrary. 
/  Decay. 

Example :  formation  of  kaolin. 
Coloration  :  mottling  of  rocks. 
Hydration.  (See  page  280.) 


Changes  other 
than  meta- 
morphism 


Sandstone  is  sometimes  changed  to  quartzite  at  the  sur- 
face by  a  process  of  weathering  or  local  meta- 
morphism. 


Limestone  and  fossils  of  lime  carbonate  change  to  crys- 
talline marble. 
Lignite  changes  to  coal. 

Coal  changes  to  anthracite,  graphite,  and  natural  coke.  f 
Changes  may  be  — 

1.  In  form  and  texture,  but  not  in  composition. 

Aragonite  to  calcite. 

Clastic  to  crystalline  rocks;  grits  to  schists. 

2.  In  chemical  composition,  by  replacement. 

Wood  to  silica. 
Calcareous  shells  to  silica. 
Effects  of  metamorphism. 

1.  Bleaching. 

2.  Change  of  color. 

3.  Hardening  and  consolidation. 

Sandstone  to  quartzite. 
Clay  and  shale  to  slate. 

*  Metamorphism  of  the  sedimentary  rocks.     By  C.  R.  Van  Hise.     16th  ann.  rep.  U.  S. 

Geol.  Surv.,  pt.  I,  683-716.    Washington,  1896. 
Metamorphism  of  rocks  and  rock  flowage.     By  C.  R.  Van  Hise.     Am.  Jour.  Sci.,  July 

1898,  CLVI,  75-91.  -  Bui.  Geol.  Soc.  Am.,  1898,  IX,  269-328. 
Physics  of  metamorphism.    By  A.  Harker.    Geol.  Mag.,  1889,  VI,  15. 
Judd.    Geol.  Mag.,  1889,  VI,  243. 
The  greenstone  schist  areas  of  ...  Michigan.    By  G.  H.  Williams.    Bui.  62,  U.  S.  Geol. 

Surv.    Washington,  1890. 

Lea  eaux  souterraines  aux  dpoques  anciennes.    Par  A.  Daubre'e.    181  et  »e.q.    Paris,  1887. 
Callaway.    Quar.  Jour.  Geol.  Soc.,  1898,  L.IV,  374.  —Am.  Naturalist,  XXXIII,  176. 


273 


274  METAMORPHISM. 

4.  Expulsion  of  water  and  vaporizable  ingredients. 

5.  Melting,  baking. 

6.  Crystallization,  with  or  without  change  in  constituent  minerals, 

including  — 
Marmarosis. 

7.  Production  of  new  minerals. 

8.  Production  of  foliation  and  schistosity. 

9.  Obliteration  of  fossil  contents. 

The  fossils  are  not  always  obliterated.* 
10.  Obliteration  of  bedding  planes. 
Causes  of  metamorphism. 

1.  Hot  waters  with  CO2  and  minerals  (alkalis)  in  solution. 

2.  Hot  vapors  and  gases  beneath  the  surface. 

3.  Movements  in  rocks,  such  as  pressure,  crushing,  and  shearing.! 

4.  Intrusion  of  hot  eruptive  rocks. 

Heat  and  moisture  are  the  chief  agents  of  metamorphism. 
Amount  of  heat. 

But  little  heat  is  necessary  to  produce  metamorphism,  and  there  are 
some  minerals  in  metamorphosed  rocks  that  can  not  withstand 
much  heat. 
Amount  of  moisture. 

But  little  moisture  is  necessary  in  metamorphism. 

Dry  heat,  however,  does  not  affect  rocks  far. 

Certain  minerals  contain  water. 
Time  an  important  element. 

The  oldest  rocks  are  usually  most  metamorphosed. 
How  heat  may  be  produced  in  rocks. 

1.  By  chemical  action. 

2.  By  the  crushing  and  shearing  of  the  rocks. 

3.  Intrusion  of  hot  rocks  from  below. 

4.  Rise  of  interior  heat.     (See  pages  136-140.) 
Metamorphism  j  Local,  or  contact. 

may  be          I  General,  or  regional. 

I.  LOCAL  OR  CONTACT  METAMORPHISM. 

Local  metamorphism  is  produced  by  the  altering  effect  of  hot  rocks  on 

those  with  which  they  come  in  contact. 
Igneous  rocks  penetrating  coal  in  southeast  Colorado  have  produced  coke 

or  powdery  graphite. 
Sometimes  other  beds  are  only  reddened. 
Limestone  much  changed  near  a  dike,  but  less  away  from  it. 

*  Daubr^e.    Geologic  experimentale.    140-142. 

t  Account  of  a  series  of  experiments  showing  the  effects  of  compression  in  modifying 

the  action  of  heat.    By  Jas.  Hall.    Edin.  Phil.  Trans.,  VI,  1812. 
Daubre'e.    Geologic  experimentale.    132. 
Adams  and  Nicolson.    Phil.  Trans.  Roy.  Soc.  London,  vol.  195,  pp.  363-401.     London, 

1901. 


275 


276  METAMORPHISM. 

A  dike  in  chalk  in  County  Antrim,  Ireland,  has  altered  the  chalk  to  the 
following  rocks,  beginning  next  to  the  dike : 

1.  Dark- brown  crystalline  limestone. 

2.  Saccharoidal  limestone. 

3.  Fine-grained  limestone. 

4.  Porcelanous  limestone. 

5.  Blue-gray  limestone. 

6.  Yellow-white  limestone. 

7.  Grades  into  chalk. 

Alteration  of  the  slates  of  the  Sierras  by  granite  dikes ;  in  places  the  meta- 
morphism  has  affected  the  rocks  as  much  as  a  mile  from  the  dikes. 
Sedimentary  beds  are  sometimes  baked  to   "  an  intensely  hard  and  ex- 
quisitely white  porcelain  "  by  a  lava  sheet.* 

These  changes  vary  greatly  in  degree,  from  incipient  metamorphism 
to  a  change  of  the  form  and  of  the  chemical  composition  of  the 
rocks. 

Experiments  of  Daubr6e.t 

Great  changes,  however,  are  not  always  produced.  Near  the  crest  of  the 
Siskiyou  Mountains,  on  the  north  side,  there  are  many  exposures  in 
the  railway  cuts,  showing  granites  containing  inclusions  that  stili 
preserve  their  bedding  planes ;  the  inclusions  are  of  all  sizes  up  to  20 
feet  or  more  in  diameter. 

II.  REGIONAL  OR  GENERAL  METAMORPHISM. J 

This  name  is  applied  to  wide  areas  where  there  is  apparently  no  connec- 
tion between  local  igneous  phenomena  and  the  metamorphism. 
Of  the  same  nature  as  local  metamorphism,  but  different  in  extent. 
Great  regions  of  schists  fall  under  this  head. 

Examples:  New  England,  Wisconsin,  Michigan,  and  Minnesota. 
North  of  Scotland.^ 
Interior  of  South  America. 
Regional,  or  general,  metamorphism  is  supposed  to  be  due  to  the  presence 

of  metamorphosing  conditions  in  rocks  over  wide  areas. 
Regional  metamorphism  is  most  common  in  regions  of  stress,  folding,  crump- 
ling, and  shearing. 

It  is  often  unequal  in  degree  and  character. 

Why  some  beds  are  metamorphosed  while  others  in  the  same  series  are  not. 
Due  to  difference  — 

1.  In  contained  water. 

2.  In  condition  of  or  size  of  the  particles. 

3.  In  composition. 

*  The  great  rift  valley.    By  J.  W.  Gregory.    137.    London,  1896. 

t  Etudes  synthetiques  de  geologic  experimentale.     Par  A.  Daubrge.     151-234.     Paris, 

|  Sur  1'origine  des  terrains  crystallins  primitifs.     Par  M.  Levy.     Bui.  Soc.  Geol.  de 

France,  XVI,  1U2-113.    Paris,  1887. 
?  On  the  metamorphosis  of  dolorite  into  hornblende  schist.      By  J.  J.  H.  Teall.     Quar. 

Jour.  Geol.  Soc.,  XLI,  133-145;  confirmed  by  John  Home,  Nature,  Sept.  19,  1901,  p. 


277 


278  METAMORPHISM. 


•/ 

METAMORPHOSED  ROCKS. 

.    .] 

All  schists,*  gneisses,  some  quartzites,  slates,  serpentines. 
Why  mountains  often  have  sediments  metamorphosed. 
They  are  regions  of  movements,  strains,  slipping,  etc. 
Why  exposed. 
By  erosion. 

They  are  often  old  rocks. 
They  are  commonly  deep-seated  rocks. 

GENERAL  CONCLUSIONS  REGARDING  METAMORPHISM. 

1.  Metamorphism  is  the  change  of  internal  form,  or  structure,  of  either 

igneous  or  sedimentary  rocks. 

2.  The  date  of  the  metamorphism  is  necessarily  later  than  that  of  the 

making  of  the  rocks. 

3.  Metamorphism  is  produced  by  — 

a.  Heat. 

b.  Pressure. 

c.  Chemical  changes  aided  by  water  and  alkalis. 

4.  Metamorphism  may  be  local  (contact)  or  regional  (widespread). 

5.  It  may  occur  in  alternate  beds  of  a  series. 

6.  It  may  affect  beds  either  vertically  or  laterally. 

7.  Regional  metamorphism  is  a  wider  extension  and  greater  development 

of  local  metamorphism . 

8.  Metamorphism  does  not  necessarily  introduce  new  chemical  elements, 

but  may  be  only  a  rearrangement  of  those  already  present. 

9.  Metamorphism  is  seldom  uniform  throughout  a  wide  area,  but  is  often 

more  intense  here,  and  less  so  there. 

10.  The  nature  of  the  changes  depends  on  — 

o.  Character  of  rocks  affected. 

b.  Nature  and  intensity  of  metamorphosing  agencies. 

11.  Metamorphic  rocks  may  be  either  old  or  new. 

Metaraorphism  is  therefore  no  test  of  the  age  of  rocks. 

12.  However,  all  the  oldest  sedimentary  rocks  are  metamorphosed,  and 

metamorphism.  is  generally  more  widespread  as  we  go  down  in  the 
geologic  series. 

13.  Metamorphism  is  most  common  in  regions  of  great  thickness  of  strata. 

14.  The  most  common  forms  of  metamorphic  rocks  are:  gneisses,  schists, 

slates,  some  quartzites,  some  marbles,  and  some  serpentines. 

15.  Metamorphism  more  frequently  takes  place  at  great  depth  below  the 

surface.    The  metamorphic  rocks  now  exposed  have,  for  the  most 
part,  been  uncovered  by  erosion. 

*  The  origin  of  glaucophane  schists.    Am.  Naturalist,  May  1901,  XXXV,  427. 


279 


280 


ROCK    CHANGES. 


REPLACEMENT. 

Of    woody    fiber    by   silica. 

(See  Plate  XIV.) 
Of    shells,   corals,    etc.,   by 

silica. 


PSEUDOMORPHISM.* 

Dehydration,     or     loss     of 
water. 


DoLOMITIZATION.t 

A  replacement  of  some  of 
the    lime    carbonate  of 

limestones  by  magnesia.        Fig.  84.— Vertical  section  in  a  quarry  at  Kilkenny, 
Ireland,  showing  both  dolomite  and  unaltered 


limestone.     (Prestwich.) 


HYDRATION. 


Anhydrite     forms     gypsum     by     taking     up 

water. i 
Peridotite  altered  to  serpentine. § 

WEATHERING. 

Changes  of  rocks  upon  exposure. || 

These  changes  are  mostly  in  the  direction  of 

disintegration    and     decomposition,     but 

i  i       j       •  Fig  85 — Horizontal  section  in 

sometimes  exposure  produces  hardening,      the  Kilkenny  quarry,  showing 


and  it  may  even  change  sandstones  into 
the  hardest  kind  of  quartzite.H 


•A  part  of    the   limestone 
(shaded)  altered  to  dolo- 
mite.   (Prestwich.) 


*  Physical  geology.    By  A.  H.  Green.    81-82.    London,  1882. 

t  Hall  and  Sardensen.    Bui.  Geol.  Soc.  Am.,  1894,  VI,  193-198. 

Klement  and  Hogbom.    Am.  Jour.  Sci.,  May  1895,  CXLIX,  426-427. 

Robert  Bell.    Bui.  Geol.  Soc.  Am.,  1894,  VI,  297-308. 

T.  C.  Hopkins.    Ann.  rep.  Geol.  Surv.  Arkansas  for  1890,  IV,  35-39.    Little  Rock,  1893. 

I  Manganese;  -its  uses,  ores  and  deposits.   By  R.  A.  F.  Penrose,  Jr.    534-536.  Little  Rock, 

I  Merrill.'   Geol.  Mag.,  Aug.  1899,  pp.  354-358. 

Holland.    Geol.  Mag.,  1899,  pp.  30-31;  540-547. 

||  Wads  worth.    Proc.  Boston  Soc.  Nat.  Hist.,  1884,  XXII,  202-203. 

Branner.    Cretaceous  and  Tertiary  geology  of  Brazil.    Trans.  Am.  Phil.  Soc.,  1889,  XVI, 

419-421. 

Hayes.  ,  Bui.  Geol.  Soc.  Am.,  1897,  VIII,  218. 
Call.    The  geology  of  Crowley's  ridge.     Ann.  rep.  Geol.  Surv.  Arkansas  for  1889,  II,  99- 

101.    Little  Rock,  1891. 


281 


282 


SPRINGS. 


Underground  Water  in  Its  Relations  to  Geologic  Structure. 
SPRINGS. 

The  waters  of  springs  are  meteoric  waters  (rain  or  enow)  that  have  fallen 
on  the  earth,  soaked  into  the  ground,  and  are  emerging  naturally.* 

Their  emergency  is  caused  by  gravity,  guided  by  the  rocks. 

Accumulations  of  water  occur  in  rocks  having  room  for  water ;  that  is,  in 
porous  rocks. 

The  porosity  is  due  to  rock  struc- 
ture, and  may  be  caused  — 

1.  By  spaces  between  coarse 

materials. 

The  coarser  the  materials 
the  more  the  space. 

Hence,  water  from  con- 
glomerates and  coarse 
sandstones. 

2.  By  joints  or  cracks  in  rocks. 

In  shales,  and  other  com- 
pact rocks,  it  flows 
through  the  joints. 

3.  By  openings  caused  by  so- 

lution   and    removal    of   Fig"  86.— Diagram  showing  in  black  the  open 
spaces  between  spheres  of  uniform  size. 

rock. 

As  in  the  caverns  of  limestone  regions. 
Note  the  size  of  springs  in  limestone  regions. 

4.  By  dolomitization  which  causes  a  shrinking  of  the  rocks. 
Water  goes  where  it  can  flow  most  easily. 

Emergence  depends  on  gravity  and  on  geologic  structure,  or  the  bedding  of  the 

rocks. 
It  may  be  caused  by  — 

1.  Fissures. 

2.  Faults. 

3.  Folds. 

4.  Impervious  strata  stopping  the  downward  passage  of  the  water 

through  overlying  porous  strata.t 

"  The  knobstone  of  southern  Indiana  is  so  compact  that  water  can  not 
pass  readily  through  it,  and  springs  are  by  no  means  common  in  that 

*  Subterranean  waters.    By  Chas.  Morris.    Jour.  Franklin  Inst.,  1901,  CLI,  182-194. 

On  the  percolation  of  rainfall,  see  The  water  supply  of  England  and  Wales.    By  C.  E. 

de  Ranee,  8-22.     London,  1882. 

Les  eaux  souterraines  a  l'6poque  actuelle.    Par  A.  Daubree.    2  vols.    Paris,  1887. 
The  principles  and  conditions  of  the  movement  of  ground  water.     By  F.  H.  King  and 

C.  S.  Schlichter.    19th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II. 
Some  principles  controlling  the  deposition  of  ores.     By  C.  R.  VanHise.     Jour.  Geol., 

Nov.  and  DPC.  1900,  VITI,  730-770. 
t  T.  C.  Hopkins.    Ann  rep.  Geol.  Surv.  Arkansas  for  1890,  IV,  345-346.    1893.  — Am.  Geol., 

1894,  XIV,  365-368. 


283 


284 


SPRINGS. 


formation.  At  the  top  of  the  formation,  however,  the  line  of  parting 
between  the  limestones  which  do  permit  the  .  .  .  circulation  of  water 
and  the  underlying  impervious  sandstone  is  a  natural  spring  horizon. 
Along  this  line  of  parting  springs  are  very  common,  and  .  .  .  they 
are  to  be  found  in  almost  every  small  side  ravine."  * 


Silurian. 


Fig.  87.— A  region  of  nearly  horizontal  rocks,  showing  the  emergence  of  springs  in  the 
ravines  and  along  the  same  stratum. 


'  J.  F.  Newsom.    Proc.  Ind.  Acad.  Sci.,  1897,  p.  256. 


285 


286 


WELLS. 


COMMON  WELLS. 

Wells  tap  rocks  holding  accumulated,  or  accumulating,  underground  waters. 
Waters  accumulate  in  any  openings  in  rock  or  soil. 

1.  Spaces  in  coarse  sediments,  gravels,  sands. 

2.  Alluvial  lands  (owing  to  position). 

3.  Pockets  in  glacial  drift.* 

TJie  uncertainty  of  water  in  the  drift  is  due  to  the  irregularity  of  the  bed- 
ding of  glacial  materials. 
Why  the  waters  of  wells  differ  even  when  near  each  other. 


Fig.  88.— Section  in  the  chalk  region  of  southwest  Arkansas,  showing  why  the  waters  of 
some  of  the  wells  are  hard  while  others  are  soft. 


Why  wells  are  sometimes  found  in  mountain  tops. 

1.  Porosity  of  containing  bed,  and  a  confining  bed  below. 

2.  Synclinal  structure  of  mountain. 
Structural  features  always  important. 

See  cases  above  mentioned. 

Synclinal  trough  south  of  Stanford  University. 

Why  water  is  abundant  on  College  Terrace,  but  not  to  be  had  in  the 

foothills  immediately  south  of  the  Quadrangle. 
Case  of  horizontal  well  in  vertical  beds. 
Where  to  bore  in  special  cases. 

ARTESIAN  WELLS.t 

Artesian  wells  are  those  from  which  the  water  flows. 

It  has  accumulated  under  special  structural  conditions. 

'*  Water  resources  of  Indiana  and  Ohio.     By  Frank  Leverett.     18th  ann.  rep.  U.  S.  Geol. 

Surv.,  pt.  IV,  419-559.    Washington,  1897. 
t  The  requisite  and  qualifying  conditions  of  artesian  wells.     By  T.  C.  Chamberlin.     5th 

ann.  rep.  U.  S.  Geol.  Surv.,  125-173.    Washington,  1885. 
Artesian  waters  of  a  portion  of  the  Dakotas.     By  N.  H.  Darton.     17th  ann.  rep.  U.  S. 

Geol.  Surv.,  pt.  II,  1-92.     Washington,  1896 
New  developments  in  well-boring  and  irrigation  in  eastern  South  Dakota.     By  N.  H. 

Darton.     18th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  IV,  561-615.    Washington,  1897. 
Artesian  wells  upon  the  great  plains  —  being  the  report  of  a  geological  commission,  etc. 

Department  of  Agriculture.    Washington,  1882. 


287 


288  WELLS. 

Wide  areas  are  usually  involved. 

Essential  conditions  for  artesian  wells  are  — 

1.  Water-bearing  stratum  (to  hold  the  water). 

Must  be  of  coarse  or  porous  material. 

2.  A  confining  stratum  (to  keep  it  in). 

Usually  fine  silts,  especially  clays. 

3.  Head  or  elevated  source  (to  force  it  out  at  the  opening). 

4.  Rainfall  at  the  outcrop  of  the  water-bearing  stratum  (to  furnish 

supply). 

Origin  of  the  artesian  waters  of  Wisconsin,  Dakota,  etc. 
Origin  of  the  Santa  Clara  county  artesian  waters. 
Importance  of  determining  elevations. 
Help  of  railway  levels  to  tie  to. 

Massive  igneous  rocks  and  granites  have  water  in  cracks  and  joints  only. 
The  uncertainty  of  finding  water  in  them  due  to  the  irregularity  of 

joints. 
Increase  of  the  flow  of  wells.* 

Periodic  fluctuations  in  the  discharges  of  artesian  wells  are  probably 

due  to  variations  of  barometric  pressure. 
The  ebbing  and  flowing  of  wells  are  attributed  to  tidal  influence  ;t  this  is 

shown  by  their  correspondence  to  be  the  case  in  some  instances. 
Periodic  discharges  may  also  be  caused  by  syphon  action  when  the 
shape  of  the  water-way  is  favorable. 

*  Outbursts  of  springs  in  time  of  drouth.     By  W.  E.  Abbott.    Jour,  and  Proc.  Roy.  Soc. 

N.  S.  Wales,  1897,  XXXI,  201-206. 

t  H.  G.  Madan.    Quar.  Jour.  Geol.  Soc.,  Aug.  1898,  LIV,  301-307. 
J.  F.  Knightly.    Geol.  Mag.,  July  1898,  p.  333. 


289 


290  PALEONTOLOGY. 


PART  III. 


HISTORICAL   GEOLOGY,  OR   PALEONTOLOGY. 


The  Order  of  Events  and  Life  as  Recorded  in  the  Rocks. 

Historical  Geology  treats  of  the  order  and  ages  of  the  rocks  —  i.  e.,  the  his- 
tory of  the  earth  as  shown  by  the  rocks  and  their  fossil  contents. 

The  history  of  the  earth  must  be  learned  — 

1.  By  deductions  from  the  known  laws  of  matter. 

2.  By  the  study  of  the  operation  of  these  laws  as  shown  by  the  rocks. 

The  laws  of  matter  teach  us  that  — 

1.  Stratified  rocks  are  laid  down  in  water  (except  seolian  and  some  plant 

accumulations)  in  approximately  horizontal  beds. 

2.  The  oldest  beds  were  laid  down  first  and  at  the  bottom,  the  newest  ones 

last  and  on  the  top. 

3.  The  disturbance  of  the  horizontality  and  continuity  of  these  beds,  and 

their  metamorphism,  must  have  taken  place  since  their  deposition. 

4.  If  a  locality  is  above  water  during  a  given  time,  no  sedimentary  beds 

can  be  deposited  thereon  during  that  period. 

5.  Inasmuch  as  the  earth's  crust  is  liable  to  elevation  and  depression, 

deposition  of  sediments  at  a  given  place  is  liable  to  be  interrupted,  and 
we  may  not  expect  to  find  a  continuous  and  uninterrupted  deposition 
at  all  places,  or  perhaps  at  any  one  place. 

6.  The  rocks  preserve  in  themselves  many  evidences  of  the  conditions  pre- 

vailing, and  of  the  geography,  when  and  where  they  were  laid  down. 

7.  The  fossils  found  in  a  given  bed  of  sediments  are  the  remains  of  plants 

or  animals  that  lived  when  the  beds  were  being  deposited.  (Except 
in  cases  of  fragments  derived  from  older  beds.) 

8.  The  periods  of  the  first  appearance  and  changes  in  the  characters  of 

faunas  and  floras  will  be  indicated,  or  suggested,  by  the  remains  of 
animals  and  plants  preserved  as  fossils. 

*  Geological  biology.    By  Henry  Shaler  Williams.    New  York,  1895. 

Text-book  of  comparative  geology.     By  E.  Kayser.      Translated  by  P.  Lake.     London, 


291 


292  FOSSILS. 

9.  In  many  places  the  sedimentary  rocks  have  all  been  removed  by  erosion, 

and  the  history  of  the  place  as  originally  preserved  in  those  rocks 

has  been  entirely  obliterated. 

It  is  thus  evident  that  the  earth's  history,  where  not  obliterated  by 
erosion  and  metamorphism,  is  to  be  found  both  in  the  nature 
and  condition  of  the  rocks,  and  in  the  character  of  the  fossils. 

10.  The  geological  record,  therefore,  is  at  best  an  imperfect  one.* 

WHAT  Is  SHOWN  BY  THE  KINDS  OF  ROCKS. 

. 

They  are  sedimentary,  organic,  chemical  deposits,  or  igneous. 
Changes  making  variation  of  rocks  often  affected  life,  and  thus  the  fossil 
contents  of  the  rocks. 

WHAT  THE  PRESENT  CONDITIONS  OF  THE  ROCKS  SHOW. 

1.  By  metamorphism,  that  they  have  been  affected  by  metamorphosing 

conditions. 

2.  By  faulting,  that  they  have  been  under  tension  or  pressure. 

3.  By  folding,  that  they  have  been  squeezed. 

4.  By  dikes,  that  molten  rocks  have  broken  through  them. 

5.  By  unconformities,  that  land  conditions,  admitting  denudation,  have 

intervened. 


Fossils  and  Their  Uses.t 

Fossils  are  the  remains  or  traces  of  plants  or  animals  imbedded  in  the  rocks. 
They  are  often  called  petrifactions,  though  they  are  not  always  petri- 
fied. 

The  word  "  fossil  "  was  formerly  applied  to  minerals,  but  it  is  no  longer  so 
used. 

WHAT  DIFFERENT  KINDS  OF  FOSSILS  SHOW. 

Salt-water  forms  show  salt-water  conditions. 
Brackish-water  forms  indicate  brackish-water  conditions. 
Fresh-water  forms  indicate  fresh-water  conditions. 
Deep-water  forms  show  deep  water. 
Shallow-water  forms  show  shallow  water. 
Cold-water  forms  show  cold  water. 
Warm-water  forms  show  warm  water. 
Swamp  life  indicates  conditions  of  swamps. 

*  Darwin's  Origin  of  species.  Chap.  X.    New  York,  1870. 

Lyell's  Principles  of  geology.    Chap.  XIV.    New  York,  1889. 

Darwinism.    By  A.  R.  Wallace.    Chap.  XIII.    London  and  New  York,  1889. 

t  Notes  on  the  siliciflcation  of  fossils.     By  T.  S.  Hunt.    Canadian  Naturalist,  2d  ser.,  I, 
46-50.    Montreal,  1864. 

Fossils,  their  nature  and  interpretation.     Geological  biology.     By  Henry  Shaler  Wil- 
liams.   78-110.    New  York,  1895. 

The  process  of  fossilization.     48th  ann.  rep.  N.  Y.  State  Museum,  II,  211-215.    Albany, 
1895. 

Fossils  and  fossilization.    By  L.  P.  Gratacap.     Am.  Naturalist,  Nov.  1896, 
912;  Dec.  1896,  XXX,  993-1003;  Jan.  1897,  XXXI,  16. 


294  FOSSILS. 

Plants  may  have  been  washed  down  in  fresh  water. 
Trees  and  big  stumps  show  land  conditions. 
Life  peculiar  to  cold  climate,  indicating  cold. 
Life  peculiar  to  warm  climate,  indicating  warmth. 
Changed  conditions  produce  variation  of  faunas  and  floras. 

These  conditions  limit  the  range  of  animals  and  plants  on  earth,  and 
hence  physical  changes  produced  different  conditions  favorable 
to  different  forms  of  life. 
In  these  changes  many  forms  were  crowded  out  and  exterminated. 

MARINE  DEPOSITS. 
Littoral. 
Deep-water. 
Abysmal. 
Animals  and  plants  having  hard  parts  often  have  them  preserved. 

Examples:  bones  of  fishes,  whales,  crabs,  corals,  shells. 
Animals  and  plants  without  hard  parts  are  seldom  preserved  as  fossils. 

Examples :  jelly-fishes,  slugs,  soft  algae. 
No  remains  are  preserved  save  when  the  conditions  are  favorable. 

LAND  DEPOSITS. 

Land  animals  and  land  plants  decay  for  the  most  part,  unless  they  fall  in 

water  or  mud,  or  are  washed  to  the  sea  and  buried  by  sediments. 
In  lakes ;  peat-bogs ;  river  mouths. 
Things  preserved  in  mud  or  clay. 

Bones,  skeletons,  teeth,  scales  of  fishes. 

Impressions    of    plants,    trunks,    bark,  and   leaves;    rain-prints, 

ripple-marks. 
Wings  of  insects. 
Birds,  bird-tracks. 
Cave  deposits ;  mammals. 
Fossils  may,  therefore,  be  — 

1.  Mold  or  impression  of  the  outside  parts  of  animal  or  plant. 

2.  Cast  of  the  inside. 

3.  The  thing  itself,  or  its  hard  parts,  preserved. 

Fossil  skin  and  hair  found  in  Siberia  and  in  Patagonia.* 

4.  The  form  of  the  thing  itself  replaced  by  some  mineral. 

Examples:  silicification  of  wood,  shells,  etc. 

These  are  petrifactions. 
Relative  values  of  fossils. 

Conditions  of  preservation  better  under  the  sea  than  on  land. 

Hence  marine  forms  are  more  abundant  as  fossils  than  land  forms, 

and  more  important. 
Some  kinds  of  fossils,  such  as  protozoa,  sponges,  and  lingulas  are 

found  in  rocks  of  all  ages. 
Others  are  very  limited  in  geologic  distribution. 

*  Bui.  Soc.  G6ol.  de  France,  1900,  XXVIII,  808. 


295 


296  THE    GEOLOGIC    COLUMN. 

Land  organisms  have  small  chance  of  preservation. 

A  body  was  found  in  a  copper  mine  in  Chile  that  had  evidently 
lain  there  since  1600  A.  D.,  preserved  by  dryness  and  by 
"  impregnation  of  the  tissues  by  copper  salts."* 

Highly  developed  and  specialized  mammals  are  of  limited  range. 


The  Geologic  Column. 

All  divisions  are  more  or  less  artificial,  for  periods  often  grade  insensibly 

into  each  other. 
What  is  meant  by  "  the  geologic  column." 

The  piling  up  of  rocks  upon  each  other. 

The  thickness  of  the  beds  varies  greatly  at  different  places. 
Attempts  to  divide  the  column  according  to  — 

1.  Lithologic  characters.^ 

Limestones,  sandstones,  clays;   are  contemporaneous  and  inter- 
grade. 

Sedimentary  and  igneous  rocks  contemporaneous. 
All  occur  from  the  bottom  to  the  top. 

2.  Color. 

"  Old  Red  "  and  "  New  Red  "  abandoned. 

Color  is  of  little  importance;  the  same  ones  may  occur  anywhere 
in  the  column. 

3.  Mineral  contents,  such  as  coal  in  the  Carboniferous. 

But  all  coal  is  not  in  the  Carboniferous. 

Minerals  are  often  introduced  as  veins  in  rocks  of  any  age. 

4.  Order  in  which  the  rocks  are  found. 

This  order  is  not  everywhere  the  same. 

Sometimes  the  newest  rocks  rest  on  the  oldest ;  sometimes  on  the 

very  new  ones. 
Difficulties    of    chronologic    division    increased    by   overturning, 

metamorphism,  faulting,  erosion,  and  interruptions  in  the 

deposition  of  the  beds. 

CORRELATION  OF  BEDS  IN  SEPARATE  REGIONS. 
What  is  meant  by  correlation. 

In  making  geologic  divisions  it  is  necessary  that  the  beds  at  one  place  shall 
be  correlated  with  those  of  another,  or  their  equivalents  determined. 
This  can  sometimes,  but  not  always,  be  done  by  tracing  the  beds 
from  one  locality  to  another. 
Precautions  necessary  in  making  correlations. 
1.  That  the  rocks  are  not  overturned. 

This  is  possible  in  regions  of  sharp  folds  and  steep  dips,  but  it  is 

not  a  common  occurrence. 
Overturns  are  decidedly  exceptional. 

*  J.  A.  W.  Murdoch.    Eng.  and  Min.  Jour.,  May  11,  1901,  p.  587. 

t  Individuals  of  stratigraphic  classification.    By  Bailey  Willis.     Jour.  Geol.,  Oct. -Nov. 
1901,  IX,  557-569. 


297 


298  CORRELATION. 

2.  That  they  are  not  faulted. 

This  is  common  in  some  tilted  regions. 

May  occur  in  horizontal  strata  bringing  similar  beds  opposite  each 
other. 

3.  Look  out  for  unconformities. 

4.  But  conforming  beds  may  not  be  continuous  deposits,  and  interven- 

ing ones  may  be  omitted. 
Color,  texture,  and  mineralogic  composition  of  bed  can  only  be  used 

within  short  distances. 
Use  of  fossils  in  the  correlation  of  rocks.* 

Beginnings  of  paleontology  by  William  Smith. 
Life  on  the  globe  has  been  changing  from  ^.he  first.* 
Each  period  has  had  its  own  forms. 
This  progress  has   involved   constantly  closer  proximity  to  existing 

forms. 
Hence,  identity  of  fossils  shows  that  the  beds  containing  them  have 

approximately  the  same  age. 

In  every  country  fossils  show  the  same  general  order  of  succession. 
Why  identity  is  only  approximate. 

1.  Slow  change  of  life  at  one  place. 

2.  Spread  of  life-forms  over  the  globe  from  one  point. 

3.  Life-zones  due  to  climatic  differences. 

4.  Life-zones  due  to  depth  and  character  of  water. 
Use  of  fossils  in  the  study  of  geographic  changes. 

Former  connection  of  America  with  Asia. 
Fossils  as  evidences  of  climatic  changes. 

Conditions  of  coral  growth  and  the  distribution  of  fossil  corals. 
Fossil  palms  found  in  cold  climates. 
Uses  of  the  knowledge  of  fossils  in  mining  geology. 

In  looking  for  coal,  or  other  rock  deposit  or  mineral,  known  to  be  at 

certain  horizons. 

Lead  and  zinc  in  the  Ozark  mountains  in  Silurian  rocks  below  Carbon- 
iferous. 

Detection  of  faults. 
Detection  of  overturns. 
Detection  of  geologic  breaks. 
Location  of  coal  beds  in  folded  areas. 

The  coal  beds  about  Magazine  mountain  and  Mt.  Nebo,  Arkansas ; 

the  Bernice  basin  in  Pennsylvania. 
Stratigraphy  will  do  the  same,  but  it  can  not  always  be  worked  out  over 

large  areas. 

Examples :  Pennsylvania,  Illinois,  east  Tennessee,  and  Alabama 
coals. 

*  The  discrimination  of  time-values  in  geology.     By  H.  S.  Williams.    Jour.  Geol.,  Oct.- 

Nov.  1901,  IX,  570-585. 
The  use  of  fossils  in  determinine  the  age  of  geologic  terranes.    By  H.  S.  Williams. 

Proc.  Am.  Assn.  Adv.  Sci.,  1889,  vol.  37,  p.  206. 


299 


Fig.  89.— Section  across  a  fault  in  the  Ozark  Mountains.    The  sandstones  at  S  are  let 

down  until  they  appear  to  be  continuous  with  the  older  ones 

below  the  Calciferous  strata. 


300 


SUBDIVISIONS    OF    THE    GEOLOGIC    COLUiMN. 


Characteristic  Life 

Period 

Man 

Psycho- 
zoic 

Recent 

Kainezoic 

Pleistocene 

Terrace 
Champlain 
Glacial 

0 

Tertiary 

SSel  Neocene 
Eocene 

Cretaceous 

Upper 
Lower 

Reptiles 

1 

Jurassic 

Middle 
Lower 

§ 

Triassic 

Upper 
Middle 
Lower 

Acrogens 
Amphibians 

Carboniferous 

Permian 
Coal  Measures 

Lower  Carboniferous 

Fishes 

Devonian 

Catskill 
Chemung 
Hamilton 
Corniferous 
Oriskany 

o 

f          Silurian 
S                   or 
•g  1     Upper  Silurian 

Lower  Helderberg 
Salina 
Niagara 

Invertebrates 

£ 

£  }        Ordovician 
OQ                   or 
L     Lower  Silurian 

Trenton 
Canadian 

Cambrian 

Potsdam 

Belt* 

Georgian 

t  Algonkian 

Keweenawan 
Huronian 

Archsea 

a             Archaean 

Laurentian 

By  C.  D.  Walcott. 


*  Pre-Cambrian  fossiliferous  formations 

1899,  X,  199-244. 
t  Van  Hise  placed  the  Algonkian  as  a  separate  formation  betw 

Paleozoic. 


Bui.  Geol.  Soc.  Am.,  Apr. 
the  Archaean  and 


301 


302  ARCHAEAN    PERIOD. 


AECH^AN  PERIOD. 

Sometimes  called  Azoic  and  Agnotozoic. 

Archaean  time  may  be  divided  into  three  periods,  or  eras. 

1.  Era  of  the  molten  globe.* 

2.  Era  of  the  cooling  crust:  condensed  vapors  covered  the  earth  with 

waters. 
If  any  part  of  the  crust  remained  above  water,  erosion  began. 

3.  Temperature  lowered  to  a  point  admitting  the  simplest  forms  of 

vegetation. 

This  was  the  beginning  of  life  on  the  earth. 
The  rocks  formed  during  Archaean  time  are  the  lowest  ones  accessible 

to  us,  and  underlie  all  others. 
Evidences  of  life  in  Archaean  rocks. 

No  fossils  are  found  in  Archaean  rocks,  but  it  seems  reasonable  to  sup- 
pose that  life  began  during  Archaean  time,  for  the  following 
reasons : 

1.  Evidences  of  life  are  abundant  in  the  next  higher  rocks  —  the  Belt 

and  the  Cambrian ;  it  is,  therefore,  reasonable  to  suppose  that 
life  had  its  beginning  somewhat  earlier. 

2.  Limestones  (marbles)  in  the  Archaean;  probably  of  organic  origin. 

3.  Iron  ores  abundant  in  Archaean ;  accumulated  through  the  agency 

of  organisms  and  organic  acids  in  bogs,  lakes,  and  meadows. t 

4.  Graphite  and  plumbago  in  Archaean  rocks  believed  to  be  derived 

from  plants. { 

5.  Apatite  is  a  phosphatic  rock.  Other  forms  of  phosphate  rocks  are  of 

organic  origin,  and  the  apatite  deposits  abundant  in  Archaean 
rocks  are  probably  metamorphosed  forms. 

6.  Presumptive  evidence. 

The  existence  of  animals  in  the  Belt  and  the  Cambrian. 
Animals  live  on  plants ;  plants  must  have  existed  first ;  animals 
of  the  Belt  must  have  had  Belt  plants,  and  those  probably 
had  Archaean  ancestors. 
The  plants  could  live  in  very  hot  waters. 
Distribution  of  Archxan  rocks  in  North  America. 
Economic  deposits  of  the  Archsean. 

Iron  ores  of  the  Adirondacks  in  New  York. 

Iron  ores  of  the  Lake  Superior  region. 

Graphite. 

Apatite  of  Canada. 

Marble  beds. 

Granites  for  building-stones. 

*  Lord  Kelvin  on  the  origin  of  granite.    By  A.  R.  Hunt.    Nature,  Feb.  22,  1900,  L.XI,  391. 
t  Phillips'  Ore  deposits.    2d  ed.    35-43.    London,  1896. 

j  On  the  graphite  of  the  Laurentian  of  Canada.  By  J.  W.  Dawson.  Canadian  Naturalist, 
new  series,  V,  pp.  13-20.    Montreal,  1870. 


303 


304  PALEOZOIC    PERIOD. 


PALEOZOIC  PERIOD. 

Nature  of  the  paleozoic  rocks. 
Mostly  marine  sediments. 
Some  fresh-water  and  land  deposits. 
Life  of  the  paleozoic  times. 

Chiefly  marine  invertebrates,  and 
Cryptogamic  plants  (ferns,  club-mosses,  horse-tails). 

Paleozoic  rocks  are  divided  (beginning  below)  into:  Belt,  Cambrian,  Ordo- 
vician  (or  Lower  Silurian),  Silurian  (or  Upper  Silurian),  Devonian, 
and  Carboniferous.  

.  Belt. 

The  word  "  Belt ' '  is  from  the  Belt  mountains  of  Montana,  where  the  rocks  of 

this  series  occur. 
Until  recently  the  Cambrian  rocks  were  considered  to  be  the  lowest  and 

oldest  containing  recognizable  fossils,  but  in  1898  Dr.  C.  D.  Walcott 

announced  the  discovery  of  the  Belt  series*  in  Montana. 
The  series  of  sedimentary  beds  is  about  12,000  feet  thick,  and  is  unconform- 

ably  below  the  Cambrian. 
It  is  composed  of  several  distinct  formations.     The  remains  of  crustaceans 

and  annelid  trails  occur  7,000  feet  below  the  unconformity. 


Cambrian. 

The  word  derived  from  "Cambria,"  the  ancient  name  of  Wales,  where 

these  rocks  were  first  studied. 
Fossils. 

No  plants  certainly  known ;  by  inference,  they  must  have  existed,  to 

supply  food  to  the  abundant  animal  life. 

Animals  include,  principally:  sponges,  hydrozoa  (graptolites),  worms, 
echinoderms,  trilobites,  gasteropods,  pelycypods,  and  brachio- 
pods. 

Ordovician  (or  Lower  Silurian). 

Name  derived  from  "  Ordovici,"  an  ancient  tribe  of  Wales,  where  these 

rocks  occur. 

The  name  "  Silurian  "  from  "Silures,"  also  an  ancient  tribe  of  Wales. 
Fossils. 

The  fossils  of  the  Ordovician  show  marked  advance  in  life. 
Some  forms,  as  graptolites  and  trilobites,  culminated  and  began  to  de- 
cline during  this  period. 

*  Pre-Cambrian  fossiliferous  formations.     By  C.    D.  Walcott.     Bui.   Geol.    Soc.  Am., 
April  1899,  X,  199-244. 


305 


306 


PALEOZOIC    PERIOD. 


Corals  rather  abundant. 

Centipedes,  the  first  known  land  animals. 

Bivalves  and  gasteropoda  increase  greatly  in  size  and  number. 

Cephalopoda  appeared  in  the  Cambrian,  but  are  abundant  in  the  Ordo- 

vician. 
Economic  products. 

Lead  ore  of  the  Galena  limestone  of  Wisconsin,  Iowa,  and  Illinois. 
Petroleum  and  gas  from  the  Trenton  limestone  of  Ohio  and  Indiana. 
Relation  of  the  "  Trenton  rock  "  to  these  products. 
Marbles  of  Vermont,  Massachusetts,  New  York,  and  Tennessee. 


Fig.  90.— Section  showing  the  geologic  structure  in  the  oil  and  gas  fields  of  Ohio. 
(Orton.) 


Silurian  (or  Upper  Silurian). 

Silurian  rocks  in  North  America  are  thicker  along  the  Appalachian  moun- 
tains, and  thin  out  toward  the  west. 

An  inland  sea  with  its  eastern  margin  near  the  eastern  border  of  the  conti- 
nent.* 
Fossils. 

Scorpions  and  insects. 
Some  plants,  but  not  abundant. 
Sharks  among  the  earliest  vertebrates. 
Crinoids  increased  in  numbers. 
Bryozoa  and  brachiopods  continue  abundant. 
Pteropods  smaller  and  less  abundant. 
Graptolites  and  trilobites  less  abundant. 
Climate. 

The  nature  of  the  fossils  suggests  warm  or  temperate  seas. 

The  occurence  of  extensive  salt  beds  in  New  York  and  Canada  shows 

that  salt  water  must  have  been  concentrated  there. 
Probably  arid  at  that  time. 

*  For  the  Silurian  areas  and  shores,  see  Stuart  Weller,  in  Chicago  Acad.  Sci.,  Bui.  IV, 
part  I,  p.  16.    June,  1900. 


307 


308  PALEOZOIC    PERIOD. 

Economic  products. 


Clinton  red  fossil  iron  ore  along  Appalachian  mountains  from  New 

York  to  Alabama. 
Joliet  building-stone  of  Illinois. 
The  brines  and  rock-salt  of  New  York  and  Canada  from  the  Salina,  or 

salt  group,  of  the  Silurian. 

Gypsum  accompanies  the  salt,  used  as  fertilizer  or  "land  plaster." 
Hydraulic  cement,  the  "  Rosendale,"  made  near  Rondout,  N.  Y. 


Devonian.* 

Name  from  county  Devon,  in  England. 
Distribution  of  Devonian  rocks  in  North  America. 

Geographic  interpretation  of  this  distribution. 

The  rocks  are  sandstones,  or  shales,  in  New  York  and  the  Appalach- 
ians, but  limestones  in  Ohio  and  Illinois. 

Thins  out  westward. 
Fossils. 

Brachiopods  the  most  abundant  fossils. 

Corals  very  large  and  abundant;  reef  forming. 

Vegetation  very  abundant. 

Fishes  remarkable  for  numbers  and  size. 

Some  Ohio  fishes  18  feet  long,  6  feet  across  head,  and  3  feet  through. 

Graptolites  and  cystids  nearly  extinct. 

First  amphibians. t 
Economic  products. 

Oil  and  gas  of  Pennsylvania  and  New  York. 

Flagstones. 

Phosphates  of  Tennessee  and  Arkansas. 

Hydraulic  limestones  at  Louisville,  Ky. 


Carboniferous. 

Name  from  the  coal  it  contains. 

The  principal  divisions  are  Permian,  Coal  Measures,  Lower  Carboniferous. 

LOWER  CARBONIFEROUS. 

Beginning  at  the  base  the  rocks  of  the  Lower  Carboniferous  are  mostly 

limestones,  and  contain  marine  fossils. 
The  area  of  these  rocks  must,  therefore,  have  been  covered  by  the  sea 

at  the  time  of  their  deposition. 
Distribution  of  Lower  Carboniferous  rocks  in  North  America. 

*  Bui.  no.  80,  U.  S.  Geol.  Surv.  Devonian  and  Carboniferous.   By  H.  S.  Williams.   Wash- 
ington, 1891. 
t  O.  C.  Marsh.    Am.  Jour.  Sei.,  Nov.  1896,  CLII,  374. 


309 


310  PALEOZOIC   PERIOD. 

Fossils. 

Crinoids  very  abundant;  some  rocks  almost  made  up  of  the  broken 
stems. 

Corals  and  brachiopods  abundant. 

Bryozoa;  Archimedes. 

Some  amphibians. 

Trilobites  decline. 
Economic  products. 

Salt  brines,  Michigan. 

Marble  of  Tennessee  and  Arkansas. 

Building-stones  of  Indiana.* 

COAL  MEASURES,  OR  CARBONIFEROUS  PROPER. 

Rocks  are  conglomerates,  sandstones,  shales,  and  coal. 

These  rocks  have  a  total  thickness  of  16,000  feet  in  Nova  Scotia;  23,780 

feet  in  Arkansas. 
No  definite  order  of  arrangement  over  the  whole  area,  but  locally  the 

order  is  constant. 
Examples :  Pottsville  conglomerate  and  Mauch  Chunk  red  shale 

in  Pennsylvania. 

Extent  of  the  Coal  Measures  in  North  America. 
The  abundance  of  coal,  and  of  fossil  plants,  show  that  the  land  was 

covered  by  extensive  marshes  for  long  periods. 
The  occurence  of  marine  fossils,  interstratified  with  coal  beds,  shows 

that  the  land  occasionally  sank  beneath  the  sea. 
The  carbon  in  the  coal  is  derived  from  the  atmosphere. 
Atmosphere  not  necessarily  heavily  charged. t 
Carbon  from  rocks  constantly  renewing  it. 
Fossils. 

Plants  are  most  abundant ;  well  preserved  in  the  clays  underlying  the 

coal  beds. 

Ferns,  club-mosses,  pines. 
Insects  abundant ;  cockroaches,  neuropters. 
Spiders. 
Amphibians. 
Economic  products. 

Coal  most  important. 

Beds  vary  from  thin  laminae  up  to  60  feet  at  Pottsville,  Pa. 

Anthracite,  bituminous,  cannel. 

Iron  ores. 

Fire-clays  associated  with  coal. 

*  Hopkins  and  Siebenthal.    21st  ann.  rep.  Geol.  Surv.  of  Indiana.    Indianapolis,  1896. 
t  Microscopical  light  in  geological  darkness.    By  E.  W.  Claypole.    Trans.  Am  Micro- 
scopical Soc.,  1897.    President's  address. 


311 


312  MESOZOIC   PERIOD. 


PERMIAN. 

Named  from  the  province  of  Perm,  Russia. 

The  division   between   the  Carboniferous  and   Permian  is  not  strongly 

marked  in  North  America. 
Distribution  of  the  rocks  in  North  America. 
Retreat  and  shallowing  of  the  Carboniferous  seas. 
The  existence  of  beds  of  salt  in  southwest  Kansas  shows  that  an  arm  of 

the  sea  was  there  cut  off  and  dried  up. 
The  structure  and  distribution  of  the  rocks  show  that  there  were  great 

geographic  changes  in  North  America  at  the  end  of  the  Permian. 
Fossils. 

Crinoids  much  less  abundant  than  in  the  Carboniferous. 

The  few  trilobites  of  the  Permian  disappear  at  the  end  of  this  period. 

First  appearance  of  reptiles. 
Economic  products. 

Gypsum  and  salt  in  Kansas. 


MESOZOIC  PERIOD. 

The  mediaeval  period  of  the  earth's  history. 

The  precise  measurement  of  the  length  of  the  periods  is  not  possible. 

The  Mesozoic  is  divided  into  Triassic,  Jurassic,  and  Cretaceous. 


Triassic.* 

Name  derived  from  the  German  rocks,  which  consist  of  three  marked  sub- 
divisions. 

In  England  the  climate  is  believed  to  have  been  arid  and  much  of  the 
country  a  desert.t 

In  North  America  the  Triassic  beds  are  marine  on  the  Pacific  coast,  fresh 
and  salt  lake  deposits  in  the  Rocky  mountain  region,  and  marine  on 
the  Atlantic  coast. 

Distribution  of  the  rocks. 

Red  sandstones  of  Massachusetts.  Connecticut,  New  Jersey,  Pennsylvania, 
Maryland,  Virginia,  and  North  Carolina. 

Some  coal  beds  in  Virginia  and  North  Carolina. 

Fossils. 

The  fossils  of  the  interior  basin  show  the  waters  to  have  been  fresh- 
water lakes. 
Those  of  the  Pacific  coast  are  marine. 

*  Bui.  85,  U.  S.  Geol.  Surv.    By  I.  C.  Russell.     Washington,  1892. 
t  Nature,  Oct.  19,  1899,  p.  610. 


313 


314  MESOZOIC   PERIOD. 

Cystids  and  blastoids  had  disappeared. 
Brachiopods  had  greatly  declined. 
Pelycypods  much  more  abundant  than  before. 
Cephalopoda  greatly  increased  in  numbers. 
Amphibia  reached  their  greatest  importance. 
Reptiles  much  more  abundant. 
First  appearance  of  mammals. 
Economic  products. 

Gypsum  and  salt  of  the  interior  basin  in  Kansas. 

Coal  beds  of  Virginia. 

Brownstone,  so  extensively  used  in  eastern  cities  for  buildings. 

Potomac  marble  of  the  Capitol  columns  at  Washington. 


Jurassic. 

The  name  from  the  Jura  mountains  in  Switzerland,  which  are  of  these  rocks. 

No  Jurassic  rocks  known  in  eastern  North  America. 

A  mediterranean  sea,  or  salt  lake,  in  the  Rocky  mountains  and  Great  Basin 

region. 

Marine  deposits  of  California  and  Oregon. 
Fossils. 

Cephalopods  culminate  in  the  Jurassic. 

Reptiles  were  very  abundant ;  some  of  them  winged ;  many  of  enor- 
mous size. 

Earliest  birds  known ;  toothed  birds. 
Economic  products. 

The  gold  veins  of  the  Pacific  slope  are  largely  in  Jurassic  slates.  These 
veins  are  not  Jurassic  in  age,  but  were  formed  subsequently. 


Cretaceous. 

Name  from  Latin  creta,  chalk. 

The  chalk  deposits  of  England  belong  here. 

Distribution  of  Cretaceous  rocks  in  North  America. 

The  geographic  changes  of  the  lower  Mississippi  valley,  that  preceded  the 

deposition  of  the  Cretaceous  beds.    Contraction  of  the  seas. 
Some  of   the  interior  beds  were  deposited  in  fresh  water;  those  of  the 

coasts  are  marine. 
Fossils. 

The  change  among  plants  is  most  marked. 

Appearance  of  dicotyledonous  plants,  with  representatives  of  oaks, 

maples,  elms,  etc. 
First  palms  known. 
Bony  fishes  very  abundant. 
Crocodiles,  mammals;  some  of  the  birds  had  teeth. 


315 


316  CENOZOIC    PERIOD. 

Economic  products. 

Greensand  marls  and  potters'  clays  of  New  Jersey. 

Chalk  deposits  of  Arkansas  and  Texas. 

Gypsum  beds  of  Iowa.* 

Coal  deposits  of  Puget  Sound,  Colorado,  Utah,  Wyoming,  Montana, 

and  New  Mexico. 

In  Colorado  these  coals  are  changed  to  anthracite. 
Auriferous  conglomerates  in  northern  California. 


CENOZOIC  PERIOD. 

The  Cenozoic  rocks  are  known  as  Tertiary,  and  Quaternary,  or  Pleistocene. 
Mammals  became  the  most  important  animals. 


Tertiary. 

Origin  of  the  name:  Paleozoic  rocks  formerly  known  as  Primary;  Meso- 

zoic  as  Secondary ;  later  ones  as  Tertiary. 
Name  retained,  though  not  used  in  its  original  sense. 
Divisions  of  the  Tertiary:  Eocene,  Miocene,  Pliocene. 

t  50%  to  90%  are  Pliocene. 
Of   living  shells  ]  30%  are  Miocene. 

(     5%  to  10%  are  Eocene. 
Distribution  of  the  seas  on  the  Atlantic  and  Pacific  coasts;  the  interior 

basins. 

Fresh-water  Pliocene  beds  of  the  Santa  Clara  valley  resting  on  marine  beds. 
The  crustal  movements  of  the  Pacific  coast. 
Warm  climate  of  Tertiary  times  is  indicated  by  plant  remains  as  far  north 

as  Greenland. 
It  has  been  suggested  that  the  warm  climate  may  have  been  due  to 

the  excess  of  carbon  dioxide  in  the  air.t 
Fossils. 

The  Tertiary  is  known  as  the  Era  of  Mammals;    but  the  Tertiary 

mammals  are  all  extinct. 
Some  gigantic.     Horses. 
Insects,  beetles,  butterflies. 
Conifers,  palms. 
Birds  abundant. 

It  is  thought  that  man  began  his  existence  in  Tertiary  times.  (See  refer- 
ences under  Psychozoic.) 

*  Gypsum  deposits  of  Iowa.    By  C.  R.  Keyes.    Iowa  Geol.  Surv.,  Ill,  pp.  259-304.    Des 

Moines,  1895. 
t  Chamberlin.    Jour.  Geol.,  Sept.-Oct.  1898,  VI,  618. 


317 


318  PSYCHOZOIC    PERIOD. 

Economic  products. 

Auriferous  gravels  of  the  Sierras. 

Diatomaceous  earths  of  California  and  of  Richmond,  Va. 

Phosphate  rocks  of  Florida  and  of  South  Carolina. 

Lignite  of  Arkansas,  Texas,  Mississippi,  California,  and  Alaska. 

Iron  ores. 

Petroleum  in  California. 

Greensand  marls  and  potters'  clay  of  the  South. 


PSYCHOZOIC  PERIOD. 


Pleistocene,  or  Quaternary. 

Man  appeared  during  this  period,  or  possibly  even  earlier.* 

Association  with  extinct  mammals. 

The  period  was  chiefly  characterized  by  glaciers  that  covered  a  large  part 

of  northern  Europe  and  the  northern  part  of  North  America. 
Climate  not  necessarily  very  much  colder;  decrease  of  5°  in  Europe  would 

bring  the  glaciers  of  the  Alps  down  to  Geneva. 
Centers  of  distribution  of  ice. 

Area  covered  at  the  greatest  development  of  the  ice.    (See  Fig.  24,  p.  92.) 
Evidences  of  glaciation ;  direction  of  movements. 
Thickness  of  the  ice. 
Withdrawal  of  the  ice. 
Evidences  of  interglacial  epochs. 

The  Wabash  drainage;  Mohawk  valley  drainage;  St.  Lawrence  drainage. 
Lake  Agassiz  and  its  history. 
Evidences  of  elevation  and  depression. 
Effect  of  glaciation  on  the  topography. 
Effect  of  glaciation  on  man. 
Extinct  gigantic  mammals. t 

*  On  the  Pithecanthropus  erectus.    By  O.  C.  Marsh.    Am.  Jour.  Sci.,  Feb.  1895,  CXLJX, 

144-147;  June  1896,  CLI,  476-482. 
t  Mammoth  and  mastodon  remains  about  Hudson  Bay.  By  R.  Bell.  Bui.  Geol.  Soc.  Am., 

1898,  IX,  369-390. 


319 


320  PSYCHOZOIC    PERIOD. 


PRIMITIVE  MAN.* 
Man  probably  originated  in  the  tropics,  where  the  climate  is  not  severe, 

where  fruits,  nuts,  and  berries  are  to  be  found  all  the  year  round; 

and  on  the  seashore,  where  fish,  mollusks,  and  crustaceans  may  be 

had  at  all  times  for  food. 
Deductions  from  zoology  concerning  man's  character  and  appearance  are 

matters  of  inference. 
Geologic  evidences  found  in  the  rocks  consist  of  — 

1.  Works  preserved. 

2.  Skeletal  remains  preserved. 
Nature  of  evidence  of  preserved  foot-prints. 

On  Carboniferous  rocks  on  the  Ohio  river. 

On  limestone  at  St.  Louis,  Mo.t 

At  Pottsville,  Pa.J 

On  lava  in  Central  America. 

HOMAN  RELICS. 
It  is  to  be  expected  that  the  oldest  traces  of  man  are  in  the  form  of  re- 

mains, for  the  earliest  men  probably  had  no  works  of  art. 
Character  of  the  relics. 

1.  Flint  implements:  arrow-heads,  knives,  spears,  chips. 

Rejects. 
Cactie  forms. 
Specialized  forms.  § 
Methods  of  manufacture.  || 
Quarries.1I 

2.  Stone  axes,  pestles,  mortars. 

3.  Carvings  on  bones  and  rocks. 

4.  Bone  and  shell  implements  and  ornaments. 

Needles  and  fish-hooks. 

5.  Pottery. 

6.  Stone  structures. 

7.  Human  bones. 

*  The  geological  evidences  of  the  antiquity  of  man.    By  Sir  Charles  Lyell.    3d  ed.,  Lon- 

don, 1863.    2d  Am.  ed.,  Philadelphia,  1863. 
The  origin  of  civilization  and  the  primitive  condition  of  man.    By  Sir  John  Lubbock. 

New  York,  1871. 
Relation  of  primitive  peoples  to  environment,  illustrated  by  American  examples.    By 

J.  W.  Powell.    Smithsonian  report  for  1895,  pp.  625-637.    Washington,  1897. 
Influence  of  environment  upon  human  industries  or  arts.    By  Otis  T.  Mason.    Smith- 

sonian report  for  1895,  pp.  639-665. 
Preadamites,  or  a  demonstration  of  the  existence  of  men  before  Adam.    By  A.  Winchell. 


5th  ed.    Chicago,  1890. 
the 


t  Owen. 
\  On  the 


Primitive  man  in  the  Somme  valley.    By  W.  Upham.    Am.  Geol.,  Dec.  1898,  XXII,  350- 
362.     (Bibliography  for  France.) 
en.    Am.  Jour.  Sci.,  1842,  XLIII,  14-32. 

the  fossil  foot-marks  in  the  red  sandstone  of  Pottsville,  Pa.    By  Isaac  Lea.    Trans. 
Am.  Phil.  Soc.,  new  ser.,  X,  307-318.    Philadelphia,  1853. 
I  Distribution  of  stone  implements  in  the  tide-water  country.    By  W.  H.  Holmes.    Am. 
Anthropologist,  Jan.  1893,  VI,  1-15.—  Wilson.    Proc.  A.  A.  A.  Sci.,  vol.  47,  p.  464. 

{Am.  Anthropologist,  1895,  VIII,  307. 
Indian  jasper  mines  in  the  Lehigh  hills.    By  H.  C.  Mercer.    Am.  Anthropologist,  Jan. 

1894,  VII,  80-92. 

Flint  implements  from  the  Nile  valley.    Nature,  April  19,  1900,  LXI,  597. 
Haworth.    Geol.  Mag.,  Aug.  1901,  VIII,  337-344;  Jan.  1902,  IX,  16-27. 


321 


322  PSYCHOZOIC   PERIOD. 

Where  these  relics  are  found. 

1.  In  caverns. 

Engis  skull  and  bones,  found  beneath  stalagmitic  crust  in  cave 
near  Liege,  Belgium,  associated  with  those  of  extinct  animals. 

Neanderthal  skull,  in  cave  near  Diisseldorf ;  probably  exceptional 
in  character. 

In  southwest  France  in  cave  with  drawings  of  mammoth,  etc. 

2.  In  peat-bogs. 

Preservative  action  of  the  peat. 

3.  In  river  and  lake  beds. 

Draining  of  Haarlem  lake  40  years  ago;  relics  were  found. 

The  Calaveras  skull  in  the  auriferous  gravels  of  California.* 

A  human  skull  said  to  have  been  found  under  the  lava  cap  of  Table 

Mountain. 
Many  human  relics  are  reported  from  the  auriferous  gravels  of 

California. 

4.  In  the  glacial  drift  and  loess. 

In  Europe  man  preceded  the  glacial  epoch. t 

Evidence  of  his  relations  to  the  glacial  epoch  in  North  America  is 
as  yet  somewhat  doubtful.* 

5.  Shell  heaps. 

Mounds  of  waste  or  kitchen-midden. 
Sites  of  ancient  settlements. 

Castro  mound ;  similar  heaps  abundant  in  the  Santa  Clara  valley 
and  on  the  coast. 

6.  Burial  mounds  or  cemeteries. 

Marajo  burial  mounds  at  the  mouth  of  the  Amazon,  and  the  pot- 
tery from  them. 

The  ornaments  developed  by  primitive  man.§ 
Generalization. 

All  the  facts  in  our  possession  go  to  show  that  primitive  man  was  a 
savage,  and  that  his  development  in  civilization  and  the  arts 
has  been  a  gradual  one. 

*  The  auriferous  gravels  of  the  Sierra  Nevada  of  California.    By  J.  D.  Whitney.    258-288. 

Cambridge,  1880,-McGee.    Science,  Jan.  20,  1899,  IX,  104,-Blake.   Jour.  Geol.,  VII, 

631-637.— Hanks.    San  Francisco,  1901. 
t  Man  in  relation  to  the  glacial  period.    By  Dr.  H.  Hicks.    Nature,  Feb.  24,  1898,  LVII, 

t  Holmes.  Jour.  Geol.,  1893,  I,  15-37,  147.— Several  papers  in  Proc.  Am.  Assn.  Adv.  Sci., 
1897,  XL VI,  344-390.— Am.  Anthropologist,  N.  S.,  I,  107-121,  614-645.— Smithsonian 
report. for  1899,  pp.  419-472. 

§  Wilson.    Ann.  rep.  Smithsonian  Inst.,  1896,  pp.  349-664. 


328 


324  GEOLOGIC    TIME. 


Length  of  Geologic  Time.* 

Difficulty  of  stating  geologic  time  in  years. 
Rate  of  the  recession  of  waterfalls. 

Age  attributed  to  the  Falls  of  St.  Anthony,  Minnesota. 

Method  of  computation.  t 

Efforts  to  compute  the  age  of  the  Niagara  gorge.  t 
Uncertain  elements  in  the  computation. 
Varying  thickness  of  the  beds. 
Different  heights  of  the  falls. 

Different  amounts  and  varying  character  of  the  water. 
Rate  of  weathering  of  cliffs.  § 
Rate  of  erosion  and  deposition. 
Rate  of  erosion  over  the  — 

Mississippi  basin  is  1  foot  for  6,000  years. 
Ganges  "      "       "      2,358    " 

Hoang-Ho  "      "       "      1,464     " 

Rhone  "      "       "      1,526    " 

Danube  "      "       "      6,846    " 

Po  "      "       "         729     " 

Mean  rate  of  the  six  "       "      3,000     " 
Ratio  of  sea-bottom  to  land  is  145  to  52,  or  say  2.8  times  as  much  water 

as  land. 

The  deposition  of  one  foot  of  sediment  would  require  8,652  years. 
The  whole  of  the  sedimentary  beds  since  Archaean  would,  at  this  rate, 

require  130  millions  of  years.|| 
Rate  of  cooling.^ 

Calculated  from  the  rate  of  cooling  rock,  the  age  of  the  earth  is  esti- 
mated at  24  millions  of  years. 

geologic  time.     By  H.  L.  Fairchild.     Proc.  Rochester  Acad.  Sci.,  1894, 

Some  geological  evidence  regarding  the  age  of  the  earth.    By  J.  G.  Goodchild.    Proc. 

Roy.  Phys.  Soc.  Edin.,  1896.  XIII,  259-308. 

Geological  biology.    By  H.  S.  Williams.    55-65.    New  York,  1895. 
Kelvin.    Philosophical  Mag.,  Jan.  1899,  XLVH,  68-90.—  Am.  Jour.  Sci.,  Feb.  1899,  pp.  160- 

165.—  Science,  May  12,  1899,  p.  665. 
Chamberlin.    Science,  IX,  889-901;  X,  11-18. 
Hunt.    Geol.  Mag.,  Mar.  1901,  VIII,  125-128. 

Joly.    Sci.  Trans.  Roy.  Dublin  Soc.,  1899,  VII,  44.—  Geol.  Mag.,  Aug.  1901,  pp.  344-350. 
Fisher.    Geol.  Mag.,  Mar.  1900,  pp.  124-132. 
I  Notes  on  subaerial  erosion  in  the  Isle  of  Skye.    By  Alfred  Barker.    Geol.  Mag.,  Nov. 

1899,  pp.  485-491. 

t  N.  H.  Winchell.    The  geology  of  Minnesota.    II,  313-341.    St.  Paul,  1888. 
\  Niagara  Falls  and  their  history.    By  G.  K.  Gilbert.    Physiography  of  the  United 

States.    203-236.    New  York,  1897.     (Brief  bibliography.) 
|  Nature,  1895,  LI,  533-607. 

\  The  age  of  the  earth.    By  Clarence  King.    Am.  Jour.  Sci.,  1893,  CXLV,  1-20. 
On  the  age  of  the  earth.    Nature,  Jan.  3,  1895,  LI,  224-227,  438-440. 
Das  Alter  der  Welt.    Von  S.  Wellisch.    Wien,  1899. 
Geikie.    Science,  Oct.  13,  1899,  X,  513-527. 

Gilbert.    Nature,  July  19,  1900,  pp.  275-278.  —  Proc.  Am.  Assn.  Adv.  Sci.,  XLIX,  1-19. 
Joly.    Geol.  Mag.,  May  1900,  VII,  220-225. 
Ackroyd.    Geol.  Mag  .  ,  Dec.  1901,  VIII,  558-559. 
Very.    Am.  Jour.  Sci.,  Mar.  1902,  CLXIII,  185-196. 


e  length  of 
II,  263-266. 


325 


326  GEOLOGIC   TIME. 

Rate  of  growth  of  corals  and  limestones. 

Estimates  from  the  rate  of  deposition  of  limestones,  etc.,  lead  Mr. 
Goodchild  to  estimate  the  age  of  the  earth  since  the  beginning 
of  Cambrian  time  at  704  millions  of  years. 

The  estimates  of  the  age  of  the  earth  since  it  was  in  a  molten  condition, 
stated  in  years,  vary  all  the  way  from  3  million  to  2,400  million 
years. 
"  Time  is  as  long  as  space  is  broad." 


327 


328  PHYSIOGRAPHY. 


PART   IV. 


PHYSIOGRAPHY,  OR  TOPOGRAPHIC  GEOLOGY.* 

Topographic  Geology  treats  of  the  surface  features  of  the  earth  in 
their  relations  to  geology. 

Topographic  forms  are  produced  by  constructive,  destructive,  and 
modifying  agencies  acting  upon  the  rocks  of  the  earth's  crust.  The  forms 
may  be  classed  as  — 

1.  The  major  relief,  or  the  continental  masses  and  ocean  basins. 

2.  The  minor  relief,  or  the  details  of  the  topography. 


THE    MAJOR   RELIEF. 

The  broad  continental  and  oceanic  features  of  the  earth  are  due  to  vertical 

movements  of  large  areas. 
These  movements  are  very  gradual. 
Theories  of  the  causes  of  mass  movements. 
1.  Loading  and  unloading. 
The  theory  of  isostacy.t 

Adjustments  must  be  slow.J 

*  The  physiography  of  the  United  States.    By  Powell,  Shaler,  Russell,  etc.    New  York, 

1897. 
Physiographic  types.    By  Henry  Gannett.    Folio  I,  Physiography.    Topographic  Atlas 

of  the  United  States.    Washington,  1898. 
Penck  gives  a  genetic  classification  of  topographic  forms  on  pages  14-17  of  Die  Geomor- 

phologie  als  genetische  Wissenschaft.  Sixth  International  Geographical  Congress. 

London,  1895. 
See  also  the  classification  of  geographic  forms  by  genesis.  By  W.  J.  McGee.  Nat.  Geog. 

Mag.,  1888, 1,  27-36. 

Earth  sculpture,  or  the  origin  of  land  forms.    By  James  Geikie.    New  York,  1898. 
Nature,  Dec.  27,  1901,  pp.  207-208. 
The  physiography  of  Allegany  county  (Maryland).    By  Cleveland  Abbe,  Jr.    Md.  Geol. 

Surv.  Allegany  county,  27-55.    Baltimore,  1900. 
The  Appalachia  region.    By  Bailey  Willis.    Md.  Geol.  Surv.,  vol.  IV,  pt.  I,  Nov.  1900, 

pp.  23-93.     (Bibliography,  p.  93.) 

Elementary  physical  geography.    By  W.  M.  Davis.    Boston,  1902. 
An  introduction  to  physical  geography.     By  G.  K.  Gilbert  and  A.  P.  Brigham.    New 

York,  1902. 
t  For  references  and  discussion,  see  Earth  movements.    By  C.  R.  Van  Hise.    Trans. 

Wis.  Acad.  Sol.,  1898,  XI,  469-475. 
On  some  of  the  greater  problems  of  physical  geology.    By  C.  E.  Dutton.    Bui.  Phil.  Soc. 

Wash.,  XI,  51-64.    Washington,  1889. 
The  great  valley  of  California,  a  criticism  of  the  theory  of  isostacy.    By  F.  L.  Ransome. 

Bui.  Dept.  Geol.,  Univ.  Cal.,  I,  371-428.    Berkeley,  1896. 
Wallace's  Malay  archipelago.    9,  foot-note.    London  and  New  York,  1894. 
U.  S.  Coast  Survey,  1894,  pt.  II,  pp.  51-55.    Washington,  1895. 
Dawson.    Quar.  Jour.  Geol.  Soc.,  1888,  XLIV,  815. 
Nature,  July  16,  1896,  LIV,  256. 
An  hypothesis  to  account  for  the  movements  in  the  crust  of  the  earth.  By  J.  W.  Powell. 

Jour.  Geol.,  VI,  1-9.    Chicago,  1898. 
Gilbert.    Bui.  Phil.  Soc.,  XIII,  61-75.    Washington,  1895.— Bui.  Geol.  Soc.  Am.,  1893,  IV, 

179-190. 
t  Coleman.    Geol.  Mag.,  Feb.  1902,  p.  61. 


330  THE    MAJOR    RELIEF. 

2.  Unequal  contraction  of  the  globe. 

Theory  of  the  early  cooling  of  the  plateaus. 
Deeper  cooling  along  depressions. 
Theory  of  differences  of  materials. 

Daubrde's  experiments  with  rubber.* 

3.  Early  tidal  action. 

Tendency  for  early  folds  to  be  permanent. 


Ocean  Basins. 

Relations  of  ocean  basins  to  the  life  of  the  glohe.t 

Relations  to  land  areas. 

Modification. 

By  deposition  — 

1.  Of  mechanical  sediments. { 

2.  Of  organic  sediments. 

3.  Of  eruptive  materials. 
By  elevation  and  depression. 

Probable  instability  of  continents  and  ocean  basins. 
Suggested  by  faunal  migrations. 

Suggested  by  elevation  of  marine  sediments,  which  is  as  great  as  the 
depths  of  the  oceans. § 


Mountains.il 

The  great  masses  of  mountain  systems  are  due  to  deformation  or  differen- 
tial elevation,  while  the  details  of  mountain  sculpture  are  produced 
chiefly  by  erosion. 

Types  of  mountains. 

1.  Mountain  chains. 

2.  Isolated  peaks. 
Geikie's  classification.^ 

1.  Original,  or  tectonic,  mountains. 

Accumulations :  volcanic  ejectamenta,  moraines,  sands. 
Deformations :  folds,  faults,  laccolites. 

2.  Subsequent,  or  relict,  mountains. 

Those  left  by  denudation. 

*  Daubree.    Geologic  experimentale.    585. 
t  J.  P.  Smith.    Jour.  Geol.,  1895,  III,  384-495. 
t  Milne.    Lon.  Geog.  Jour.,  1897,  X,  259-289. 

I  References  in  Geikie's  Text-book  of  geology.    3d  ed.,  1070.    New  York,  1893. 
Gilbert.    Bui.  Geol.  Soc.  Am.,  1893,  IV,  187. 

La  question  de  la  permanence  ou  de  I'instabilite'  des  grandes  depressions  oc^aniques. 
Par  F.  Prien.    Annales  de  Geographic,  III,  173-182.    Paris,  1893-94. 

II  Die  Hochgebirge  der  Erde.    Von  Robert  von  Lendenfeld.    Freibunr,  1899. 

\  Mountains.    Ey  James  Geikie.    Scottish  Geog.  Mag.,  Sep.  1901,  XVII,  449-459. 


331 


332          '  THE    MINOR    RELIEF. 


MOUNTAIN  CHAINS. 

Theories  of  the  origin  of  mountain  chains.* 

1.  Arching  of  the  rocks.     (Deformation.)t 

2.  Rise  of  isogeotherms  through  sediments. 

3.  Outflows  of  lava. 

a.  Due  to  relief  of  pressure  by  arching. 

b.  Due  to  relief  by  tensile  movements. 

The  fusion  point  is  lowered  in  both  cases. 

4.  Permanency  of  folds,  however  produced. 

5.  Faults. 

Location  of  faults  of  California  with  reference  to  the  Sierras  and 
Coast  ranges.*    (See  Plate  XXV.) 

ISOLATED  PEAKS. 

1.  Culminating  points  in  mountain  chains. 

2.  Constructed  by  volcanic  ejectamenta. 

San  Francisco  mountains ;  Flagstaff,  Arizona. 
Jorullo,  Mexico,  made  in  a  night  (1,692  feet).§ 

3.  Mountains  or  peaks  left  by  circumdenudation. 

Enchanted  mesa  and  the  buttes  of  that  type. 
(See  also  page  48  and  Plate  XXIV.) 


MINOR  RELIEF. 

Relief  forms  may  be  built  up  by  construction,  may  be  produced  by  some 
modification  or  superinduced  structure,  or  they  may  be  the  results 
of  destructive  agencies  acting  upon  land  masses. 

The  agencies  may,  therefore,  be  classed  as  constructive,  modifying  and  de- 
structive. 

*  The  origin  of  mountain  ranges.    By  T.  Mellard  Reade.    London,  1886. 

Orographic  geology,  or  the  origin  and  structure  of  mountains.    By  G.  L.  Vose.    Boston, 

1866. 
Etudes  des  alignements.    Par  M.  de  Chancourtois.    Congres  Internal,  de  Geologic,  1878, 


pp.  43-52. 
plan  of  th 


The  plan  of  the  earth  and  its  causes.    By  J.  W.  Gregory.    Am.  Geol.,  Feb.  1901,  XXVII, 

100-119;  Mar.  190],  pp.  134-147. 

Theory  of  the  origin  of  mountain  ranges.    By  J.  Le  Conte.    Jour.  Geol.,  1893,  I,  543-573. 
The  tetrahedral  earth  and  zone  of  the  intercontinental  seas.    By  B.  K.  Emerson.    Bui. 

Geol.  Soc.  Am.,  1900,  XI,  61-106. 

t  Willis.    13th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  249. 
t  The  great  Sierra  Nevada  fault  scarp.    By  H.  W.  Fairbanks.    Pop.  Sci.  Monthly,  Mar. 

1898,  LII,  609-621. 
I  Voyage  de  Humboldt  et  Bonpland.    Atlas  pittoresque.    242-244.    Paris,  1810. 


Plate  XXV.  —  Photograph  of  Dr.  Drake's  relief  map  of  the  State  of  California, 

showing  the  northwest-southeast  axes  of  the  valleys, 

partly  due  to  faulting. 


333 


334 


THE    MINOR    RELIEF. 


I.  Constructive  Agencies  and  the  Forms  They  Produce.* 

Subaqueous  forms. 

Widespread  deposits. 
Deltas.     (See  page  52.) 
Bars.     (See  page  74.) 
Barrier  beaches.     (See  page  76.) 
Spits.     (See  page  74.) 
Emergent  forms . 

Transformation  of  deltas,  bars,t  barriers,  and  spits  into  dry  land.* 
Case  of  Interlaken;   Gulf 

of  California. 
A  delta  on  a  rising  shore. 
Silting  up  of  fjords. 

Example:  Oceanside,  Cal- 
ifornia. 

Silting     up    of     lakes;     salt 
marshes  and  fresh- water 
marshes. § 
Formation  of  storm  beaches; 

coral  islands. 
Subaerial  forms. 

^Eolian  deposits. 
Volcanic  ejectamenta. 
Cinder  cones. 

Near  Flagstaff,  Arizo- 
na ;  in  San  Bernar- 
dino county,  Cal. 
Lava  cones. 

Examples :       Shasta ; 

Marysville  buttes. 
Laccolitic  mountains.  || 
Lava  sheets. 

Example :  Wyoming,  Idaho,  etc. 

Calcareous  and  siliceous  deposits  formed  by  certain  springs  and  streams. 
Alluvial  cones. 

*  The  topography  of  Florida.  By  N.  S.  Shaler.   Bui.  Mus.  Comp.  Zool.,  XVI.  Cambridge, 

1890. 

t  On  the  forms  of  certain  deltas.    Daly.    Science,  June  14,  1901,  XIII,  952-954. 
t  An  interesting  case,  partly  attributable  to  elevation  and  partly  to  emergence  from 

delta  accumulations,  is  that  of  the  Isthmus  of  Suez  filled  in  as  a  part  of  the  Nile 

delta,  and  separating  Asia  from  Africa.  See  Hull's  Survey  of  western  Palestine,  72. 
Beitriige  zur  Morphologie  der  Flachkiisten.  Inaug.  Diss.  von  Karl  Weule.  Weimar,  1891. 
Shore-line  topography  By  F.  P.  Gulliver.  Proc.  Am.  Acad.  Arts  and  Sci.,  Jan.  1899, 

XXXIV,  151-258. 
I  Fresh-water  morasses  of  the  United  States.    By  N.  S.  Shaler.    10th  ann   rep.  U.  S. 

Geol.  Surv.,  261-339.    Washington,  1890. 

The  dikes  of  Holland.    By  G.  H.  Mathes.    Nat.  Geog.  Mag.,  June  1901,  XII,  219-234. 
||  Geology  of  the  Henry  mountains.    By  G.  K.  Gilbert. 
The  laccolitic  mountain  groups  of  Colorado,  Utah,  and  Arizona.    By  W.  Cross.    14th 

ann.  rep.  U.  S.  Geol.  Surv.    157-241.    Washington,  1895. 


Fig.  91.— Sketch  map  showing  the  submerged 

and  choked  up  valleys  near  Oceanside, 

California. 


335 


THE    MINOR   RELIEF. 


Folding. 
Faulting.* 


II.  Deformation,  or  Modifying  Agencies. 


III.  Destructive  Agencies. 

I.  Atmosphere,  by  means  of  — 

1.  Atmospheric  moisture. 

2.  Winds. 

3.  Changes  of  temperature. 

II.  Water  in  form  of  — 

1.  Rain. 

2.  Springs. 

3.  Streams. 

4.  Waves. 

5.  Glaciers. 

6.  Tidal  currents,  t 

THE  FORMS  PRODUCED  BY  DESTRUCTIVE  AGENCIES,  AND  THE  FACTORS  DE- 
TERMINING THEM. 

The  forms  produced  by  destructive  agencies,  other  things  being  equal, 
depend  upon  several  controlling  factors,  which  may  act  alone  or  in 
combination.* 

CONTROLLING  FACTORS. 

I.  The  character  and  alternation  of 

the  rocks. 
Erosion  avoids  the  hard  and 

seeks  the  softer  rocks. 
Harder  sandstones  resist, 

and  make  ridges. 
Softer    shales    and    clays 
yield,  and  make  valleys. 
Soluble  limestones  are  carried 
off  in  solution,  leaving 
caves  and  sink-holes. 
In  regions  of  alternate  hard 
and  soft  beds,  the  topog- 
raphy is  controlled  more 
or  less,  according  to  cir- 
cumstances, by  the  difference  in  the  resisting  powers  of  the  rocks. 

*  Origin  and  structure  of  the  Basin  ranges.    By  J.  E.  Spurr.    Bui.  Geol.  Soc.  Am.,  1901, 

The  ranges  of  the  Great  Basin.    By  W.  M.  Davis.    Science,  Sept.  20,  1901,  XIV,  457. 
Physiographic  evidence  of  faulting.    By  W.  M.  Davis.    Science,  Sept.  20,  1901,  XIV,  458- 

t  Tidal  erosion  in  the  Bay  of  Fundy.    By  G.  F.  Matthew.    Canadian  Naturalist,  new 

ser.,  1881,  IX,  368-373. 
J:  Denudation  with  reference  to  ...  configuration,  etc.    By  A.'  B.  Wynne.    Geol.  Mag., 

IV,  3-10.    London,  1867. 


Fig.  92.— A  smooth  surface  of  alternate  hard 
and  soft  (shaded)  strata  standing  on  end. 


Fig.  93.— The  same  as  Fig.  92  after  being  sub- 
jected to  denudation.    The  streams 
follow  the  soft  beds. 


337 


5  THE    MINOR    RELIEF. 

Influence  of  the  varying  character  of  sediments  on  the  continuity  of 

ridges  and  valleys. 
Origin  of  "  pulpit  rocks,"  "chimney  rocks,"  "table  rocks,"  "bottle 

rock."*     (See  Fig.  98.) 
Exceptional  character  of  the  Tepee  buttes.t 


Fig.  94.— Profile  of  bench-and-bluff 
topography  yielded  by  alter- 
nate hard  and  soft  beds. 


Fig.  95. — A  bluff  of  homogeneous  soft 
with  a  single  bed  of  hard  rock. 
(Harris.) 


Fig.  96.— Bench-and-bluff  topography  in  a  region  of  horizontal  beds.    (Simonds.) 

II.  The  geologic  structure  or  position  of  the  beds. 

Influence  of  the  slope  of  the  beds  on  the  character  of  the  topography. 

Topography  of  horizontal  beds. 

Bench  and  bluff  topography.     (See  Figs.  96  and  97.) 
Grand  canon  of  the  Colorado. 
Mountains  and  hills  of  circumdenudation.t 

Enchanted  mesa.     (See  Plate  XXIV.) 


Fig.  87.— Diagram  representing  a  section  across  an  anticline,  and  showing  the  influence 
of  the  fold  upon  the  topography. 

*  Excellent  illustrations  by  Gould  in  Trans.  Kansas  Acad.  Soi ,  XVII,  plates  IX  X  XI 

Topeka,  1901. 

t  Tepee  buttes.    By  Gilbert  and  Gulliver.    Bui.  Geol.  Soc.  Am.,  1895,  VI,  333-342. 
t  The  Enchanted  Mesa.    By  F.  W.  Hodge.    Nat.  Geog.  Mag.,  VIII,  273-284.   Washington, 


339 


Fig.  98.— A  "  pulpit  rock,"  left  by  the  removal  of  the  adjacent  horizontal  strata. 
(Hopkins.) 


340 


THE    MINOR    RELIEF. 


Fig.  99.— Sketch  map  showing  the  relation  of  folded  and  denuded  beds  of  rock  to 
topography.     (Means.) 

Topography  of  folded  beds.* 

Arkansas,  t  • 

Colorado. 
Seashore  topography  varying  with  the  position  of  the  beds  in  relation 

to  the  waves. 

Topography  of  eruptive  dikes.* 
Influence  of  dip  on  the  lateral  movements  of  streams.     (See  page  354.) 

III.  Jointing  or  fracturing  of  the  rocks. 

Influence  of  lines  of  weakness  produced  by  joints  and  other  breaks. § 
Zig-zags  of  Cheddar  gorge. H 

IV.  The  slope,  of  the  land  surface. 

The  transporting  power  of  a  stream  varies  with  the  sixth  power  of  the 

velocity. 
Velocity  is  determined  by  the  slope.   It  follows  that  the  rate  of  cutting 

is  determined  by  the  slope. 

Influence  of  settling  basins  on  the  work  of  streams. 
Examples :  Great  Lakes  and  the  St.  Lawrence. 

*  Manual  of  coal  and  its  topography.    By  J.  P.  Lesley.    Philadelphia,  1856. 

Some  illustrations  of  the  influence  of  geological  structure  on  topography.    By  Benjamin 

Smith  Lyman.    Jour.  Franklin  Inst.,  May  1898,  CXLV,  355-360. 
t  Physiographic  geology  of  western  Arkansas.    By  Arthur  Winslow.    Bui.  Geol.  Soc. 

Am.,  1891,  II.  225-242. 

1  Spanish  Peak  folio,  U.  S.  Geol.  Surv.,  no.  71. 

I  Dutton's  High  plateaus  of  Utah.    Plate  VII,  253;  plate  X,  280.    Washington,  1880. 
Daubre'e's  Geologic  experimentale.    300-374.    Paris,  1879. 
Erosion  forms  in  Harney  Peak  district,  South  Dakota.    By  E.  O.  Hovey.    Bui.  Geol.  Soc. 

Am.,  1899,  XI,  581-582. 
|  Callaway.    Geol.  Mag.,  Feb.  1902,  IX,  67-69. 


341 


342 


THE    MINOR    RELIEF. 


Fig.  100. — The  "  hogbacks  "  at  Morrison,  Colorado.    The  Rocky  Mountain  range  is  on 
the  right  and  the  rocks  dip  eastward  away  from  it. 

V.  Climatic  conditions. 

Minor  topographic  features  mostly  carved  by  water. 

Regions  without  water  subject  to  little  or  no  change  from  this  cause. 

Blown  sands  of  arid  regions. 

Origin  of  "hog- wallows."* 

Effect  of  frost  and  moisture  on  rocks  easily  disintegrated. 

Example :  "  Knobstone  "  of  Indiana  has  gentle  slopes  facing  south- 
ward. 
Deserts.t 

VI.  Interruptions  in  development. 

The  process  of  topographic  development  may  be  hastened,  retarded,  or 
entirely  changed,  by  — 

1.  Landslides  damming  up  streams  and  shifting  divides. 

2.  Faults  across  streams  producing  falls,  cataracts,  or  lakes. 

Examples:  American  valley,  Calaveras  valley,  Sierra  valley. 

3.  Lava  flows  damming  streams,  and  diverting  the  old,  or  imposing 

a  new  drainage. 

*  Turner.     17th  ann.  rep.  U.  S.  Geol.  Surv.,  part  I,  681-684.    Washington,  1896. 

J.  Walther.    Die  denudation  in  der  Wiiste.    377.    Leipzig,  1891. 

Hog-wallows,  or  prairie  mounds.    By  J.  Le  Conte.    Nature,  Apr.  19,  1877,  XV,  530-531. 

Across  the  Vatna  Jokull.    By  W.  L.  Watts.    76. 

The  hillocks,  or  mound  formations,  of  San  Diego,  California.    By  G.  W.  Barnes.    Am. 

Nat.,  Sept.  1879,  XIII,  565-571. 
t  Lapparent.     Annales  de  Geographic,  V,  1-14.    Paris,  1895-96. 


344  THE   MINOR    RELIEF. 

4.  Glaciation  filling  old  depressions,  scooping  out  basins,  and  com- 

pelling a  new  drainage.* 
Moraines  damming  water  in  valleys. 
Donner  lake. 
Seattle  lake. 
Kettle  moraine  region  of  Wisconsin  and  Minnesota. 

5.  Depression  carrying  the  region  beneath  the  sea. 

The  origin  of  fjords  and  harbors.t 

VII.  The  primitive  drainage. 

Sinking  of  land  beneath  the  sea,  and  the  deposition  of  new  beds  upon 

the  old  topography. 
When  such  areas  are  re-elevated  the  drainage  of  the  new  surface  is 

determined  by  general  slope  and  local  accidents. 
Cutting  their  channels  downward,  the  streams  reach  and  uncover  the 

buried  topography. 

The  channels  are  already  determined,  however. 
Such  drainage  is  said  to  be  superimposed. 
In  the  main,  it  is  often  quite  independent  of  the  geologic  structure  in 

which  it  ultimately  flows. 
There  is  a  tendency,  however,  for  such  drainage  to  come  more  and 

more  under  the  influence  of  the  geology. 

VIII.  The  length  of  time  the  region  is  exposed  to  erosion. 
Erosion  attacks  all  land  surfaces. 

It  follows  that  the  longer  these  surfaces  are  exposed  to  erosion,  the 

more  they  are  eroded. 
Topography  of  any  area,  therefore,  changes  constantly. 


Cfl    »    B     SC  ^J 


Fig.  101.— Diagrams  illustrating  the  structures  shown  by  the  wearing  down  of  an 
overturned  anticline.    (Ashley.) 

*  Glacial  origin  of  certain  lakes  of  Switzerland.    By  A.  C.  Ramsay.    Quar.  Jour.  Geol. 

Soc.,  1862,  XVIII,  185-204. 
Physical  geology  and  geography  of  Great  Britain.    By  Sir  A.  C.  Ramsay.    8th  ed.,  264- 

275.    London,  1894. 
Glacial  erosion.    By  W.  M.  Davis.    Proc.  Boston  Soc.  Nat.  Hist.,  XXII,  19-58.    Boston, 

1884. 
t  The  geological  history  of  harbors.    By  N.  S.  Shaler.    13th  ann.  rep.  U.  S.  Geol.  Surv., 

part  II,  93-209.    Washington,  1893 
Topographisch-geologische  Studien  in  Fjordgebieten.    Von  Otto  Nordenskjold.    Bui. 

Geol.  Inst.,  Univ.  Upsala,  1899,  IV,  157-226.    Upsala,  1900. 
On  the  physical  history  of  the  Norwegian  fjords.    By  E.  Hull.    Geol   Mag.,  Dec.  1901, 

VIII,  555-558. 


345 


346  VALLEYS. 

Waterfalls  are  new  topographic  features,  and  must  disappear  in  time. 
In  general,  there  is  a  tendency  to  smooth  down  irregularities,  and  to 

reduce  all  to  a  common  low  level. 
Peneplains  or  base-levels  of  erosion.* 
The  geographical  cycle.t 

IX.  The  nature  and  working  methods  of  the  eroding  agency. 
Erosion  is  done  mostly  by  water  and  ice  in  motion. 
Erosion  done  by  water  tends  to  cut  deep,  narrow  gullies  and  gorges  on 

the  land,  and  to  undercut  sea  and  lake  shores,  and  to  spread  out 

silts  over  flood-plains  and  sea-bottoms. 
Erosion  by  ice  tends  to  round  off  small  surface  irregularities,  while  its 

load  is  left  in  the  form  of  moraines. 
Erosion  in  arid  regions  by  isolation  and  deflation  4 


Valleys. 
General  forms. 

1.  V-shaped  and  inverted-A-shaped. 

2.  U-shaped. 

3.  With  gently  sloping  sides. 

VALLEY-FORMING  AGENCIES. 

1.  Erosion. 

Most  of  our  narrow  valleys,  canons,  gulches,  gorges,  ravines,  etc.,  have 

been  made  by  this  agency. 
These  are  mostly  steep-sided. 

Examples :  Yosemite,§  Tuolumne,  Colorado. 
The  U-shape  of  valleys  often  attributed  to  ice  action. || 

2.  Folding. 

Example :  Lackawanna-Wyoming. 

3.  Faulting.^ 

Examples:   northern  California  and  Oregon  Coast  ranges  and  their 

paral  1  el  valley s .     (See  Plate  XXV . ) 
Valleys  are  not  always  washed  out  along  fault-lines. 

4.  Building  up  the  sides. 

Such  valleys  lie  between  volcanic  mountains. 

Examples:  central  France;  Hawaii. 
Construction  by  moraines. 

Seattle  and  Tacoma  maps. 

*  Tarr.    Am.  Geol.,  June  1898. 

Daly.    Am.  Nat.,  Feb.  1899,  XXXIII,  127-138. 

Davis.    Am.  Geol.,  Apr.  1899,  XXIII,  207-239.  -  Jour.  Geol.,  1902,  X,  77-111. 

Shaler.    Bui.  Geol.  Soc.  Am.,  1899,  X,  263-276. 

t  Davis.    International  Congress  of  Geography.    Berlin,  1900. 

t  Earth  sculpture.    By  James  Geikie.    250-265.    New  York,  1898. 

I  The  Pleistocene  geology  of  the  ...  Yosemite  Valley.    By  H.  W.  Turner.    Proc.  Gal. 

Acad.  Sci.,  3d  ser.,  I,  261-321.    San  Francisco,  1900. 

II  Die  Hochketten  des  nordamerikanischen  Felsengebirges  u.  der  Sierra  Nevada.    Von 

Dr.  E.  Deckert.  Sonder-Abdr.  a.  d.  Zeitsch.  der  Gesells.  f.  Erdkunde  zu  Berlin, 
Mar.  1901,  XXXVI,  162. 

\  Valleys  and  their  relations  to  fissures,  fractures  and  faults.  By  G.  H.  Kinahan.  Lon- 
don, 1875. 

The  rift  valleys  of  eastern  Sinai.    By  W.  F.  Hume.    Geol.  Mag.,  1901,  VIII,  198-200. 


347 


348 


Fig.  103.— The  glaciated  narrow  canon  of  the  Tuolumne  river  west  of  Poopenaut 
valley,  Sierra  Nevada  Mountains.    (Turner.) 


Fig.  103.— Profile  of  the  glaciated  gorge  between  the  Camp  Bird  mine  and  Ouray, 
Colorado.    (Purdue.) 


349 


Fig.  104.— Profile  of  the  Animas  canon  below  Silverton,  Colorado.    This  gorge  was 
filled  with  ice  during  the  glacial  epoch.    (Maofarlane.) 


H-J- 


Fig.  105.— Profile  of  the  V-shaped  Animas  canon  two  miles  below  Silverton, 
Colorado.    (Macfarlane.) 


350  LAKES. 

AGENCIES  MODIFYING  VALLEYS. 

I.  Ice  erosion  and  moraines. 

Examples:  Yosemite,  Lackawanna. 

II.  Filling  in  when  dammed  up. 
Examples:  Calaveras,  American,  Sierra. 


Lakes.* 

Lake  basins  originate  in  some  of  the  following  ways : 

1.  Scooping  out  of  basins  by  glaciers. t 

2.  Damming  back  the  waters  by  — 

a.  Landslides. t 

b.  Existing  glaciers. § 

v         c.    Moraines  left  across  valleys. 

Lake  Chelan  in  northern  Washington  is  50  miles  long,  and 
from  a  half  to  one  mile  wide,  1,400  feet  deep  in  the  mid- 
dle, is  dammed  at  its  lower  end  by  a  moraine. || 

Moraine-dammed  lakes  in  Norway. if 

d.  Igneous  outflows  across  the  drainage. 

Nicaragua.** 
Tahoe.tt 

e.  Faults  rising  across  the  drainage. 

/.   Shore  accumulations,  or  cordon  littoral.tt 
g.  Sand-dunes. 

*  Les  lacs  de  Jura.    Par  Ant.  Magnin.    Ann.  de  G6og.,  1894,  III,  213-226. 

Lakes  of  North  America.    By  I.  C.  Russell.    Boston,  1895. 

The  English  lakes.    By  H.  R.  Mill.     Geog.  Jour.,  July-Aug.  1895. 

Present  and  extinct  lakes  of  Nevada.    By  I.  C.  Russell.    Physiography  of  the  United 

States,  101-136.    New  York,  1897. 
Jour.  Geol.,  1896,  IV,  647-648. 
An  account  of  the  researches  relating  to  the  Great  Lakes.  By  J.  W.  Spencer.  Am.  Geol., 

Feb.  1898,  XXI,  110-123. 
The  formation  and  deformation  of  Minnesota  lakes.    By  C.  W.  Hall.    Science,  1893,  XXI, 

314. 

Les  lacs  francais.    Par  Andre  Delebecque.    Paris,  1898. 
The  scientific  study  of  scenery.    By  J.  E.  Marr.    158-202.     London,  1900. 
t  On  the  origin  ...  of  the  basins  of  the  Great  Lakes.    By  J.  S.  Newberry.    Proc.  Am 

Phil.  Soc.,  1882,  XX,  91-101. 

Spencer.    Quar.  Jour.  Geol.  Soc.,  1890,  XLVI,  523-533. 
Bonney.    Geol.  Mag.,  Jan.  1898,  pp.  15-20. 
Parkinson.    Geol.  Mag.,  Mar.  1901,  VIII,  97-101. 
Winchell.    Bui.  Geol.  Soc.  Am.,  1901,  XII,  109-128. 

1  Topographic  features  due  to  landslides.    By  I.  C.  Russell.    Pop.  Sci.  Monthly,  Aug. 

The  landslip  at  Gohnah,  India.    Nature,  July  5,  1894,  L,  231-234,  428,  501. 

2  Russell.     13th  ann.  rep.  U.  S.  Geol.  Surv.,  pt.  II,  76-80. 

||  Henry  Gannett.    Nat.  Geog.  Mag.,  Oct.  1898,  IX,  417-428. 

H  Monckton.    Geol.  Mag.,  Dec.  1899,  pp.  533-540. 

**  Geology  of  Nicaragua  canal  route.    By  C.  W.  Hayes.    Bui.  Geol.  Soc.  Am.,  X,  340. 

ft  Lindgren.    Folio  39,  U.  S.  Geol  Surv.,  1897.  —  Jour.  Geol.,  1896,  IV,  895. 

n  Les  lacs  francais.    Par  Andre  Delebecque.    Plates  XVII,  XVIII,  XIX,  280-284.    Paris, 


351 


352  STREAMS. 

3.  Cutting  off  of  basins  by  silting  up. 

Examples:  Saltonlake;*  Interlaken,  Switzerland ;  Vale  of  Kash- 
mir.f 

4.  Shifting  of  streams. 

Ox-bows  of  the  Mississippi  river. 

5.  Orographic  movements. 

fi.  Depressions  caused  by  solution  of  rocks. 

Sink-holes  and  ponds  of  limestone  regions  of  Tennessee,  Kentucky, 

etc. 
7.  Extinct  craters. 

Crater  Lake,  Oregon.* 
West  side  of  Mt.  Hood. 

Generalization:  lakes  are  temporary  features,  and  are  constantly  being 
formed  and  obliterated. 


Streams  and  Their  Changes.^ 

The  age  of  streams. 

Newer  than  the  beds  over  which  they  flow. 

Importance  of  initial  conditions. 
Consequent  streams. 

Streams  whose  positions  are  determined  by  the  slope  of  a  new  surface. 

Subsequent  development  depends  chiefly  upon  the  geology. 

Regions  of  horizontal  rocks. 

Regions  of  folded  rocks. 

Influence  of  rock  joints. || 

Shifting  of  channels  due  to  dip.     (See  Figs.  106  and  107.) 

Shifting  of  channels  due  to  choking  by  debris.  If 

*  Sal  ton  Lake.  By  E.  B.  Preston,  llth  ann.  rep.  State  Mineralogist  of  Cal.,  387-393. 
Sacramento,  1897. 

t  Climbing  and  exploration  in  the  Karakorum-Himalayas.  By  W.  M.  Conway.  37.  New 
York,  1894. 

t  Crater  Lake,  Oregon.  By  J.  S.  Diller.  Nat.  Geog.  Mag.,  VIII,  33-48.—  Smithsonian  rep. 
for  1897,  pp.  369-379.  —  Science,  Feb.  7,  1902,  pp.  203-211. 

Mazama.    I,  139-393.    Crater  Lake  number.     Portland,  Or.,  1897. 

§  On  the  physical  features  of  the  Valley  of  the  Colorado.  Part  II,  147-214,  of  The  explora- 
tion of  the  Colorado  River  of  the  West.  By  J.  W.  Powell.  Washington,  1875. 

The  rivers  of  northern  New  Jersey.  By  W.  M  Davis.  Nat.  Geog.  Mag.,  II,  81-110.  Wash- 
ington, 1890. 

The  rivers  and  valleys  of  Pennsylvania.  By  W.  M.  Davis.  Nat.  Geog.  Mag.,  I,  183-253. 
Washington,  1889. 

Lecons  de  geographic  physique.     Par  A.  de  Lapparent.     109-130.    Paris,  1896. 

Drainage  modifications  and  their  interpretation.    By  M.  R.  Campbell.    Jour.  Geol.,  1896, 

How  rivers  work.    The  physical  geography  of  New  Jersey.    By  R.  D.  Salisbury.    70-82. 

Trenton,  1898. 
Rivers  and  river  valleys.    Aspects  of  the  earth.    By  N.  S.  Shaler.    143-196.    New  York, 

River  adjustments  in  North  Carolina.    By  W.  J.  Weaver.    Jour.  Elisha  Mitchell  Sci 

Soc.,  1896,  pp.  13-24. 

Rivers  of  North  America.    By  I.  C.  Russell.    New  York,  1898. 
I  The  river  system  of  Connecticut.    By  W.  H.  Hobbs.    Jour.  Geol.,  Sept.-Oct.  1901,  IX, 


H  Davis.    Bui.  Mus.  Comp.  Zool.,  XXXVIII,  Geol.  series,  V,  135.    Cambridge,  1901. 


353 


354 


Fig.  106.-A  smooth  surf  ace  of  hard  and  soft 
(shaded)  inclined  beds. 


Fig.  107.— The  same  as  Fig.  106  after  being 

subjected  to  erosion.    The  streams 

follow  the  soft  strata. 


Fig.  108.—  A  region  of  folded  bed 
streams  follo 


Superimposed  streams. 

Superimposed    streams    have 
cut  down   from    initial 
conditions     that     were 
developed  regardless  of 
the  present  structure. 
Example :  southArkansas. 
Antecedent  streams. 

Antecedent  streams  are  those 
that  hold  and  cut  their 
way  through  obstacles 
rising  across  their 
courses. 

New  cycles  of  erosion  are  brought 

about  by  interruptions  of  a 

system  of  drainage. 

The  winding  of  upland  streams. 

Superimposed ;  developed 

drainage.* 

The  winding  of  lowland  streams. 
Stream  capture. 

TERRACES,  t 

Terraces  may   be  produced  by — 

1.  The  cutting  of  waves  along  a  shore. i 

2.  The  cutting  of  a  meandering  stream. § 

Why  the  highest  terraces  are  the 

oldest. 
Why  stream  terraces  are  often  in 

pairs. 

3.  The  differential  resistance  (to  eros- 

ion) of  horizontal  beds  (rock  ter- 
races). 

4.  Streams  truncating  alluvial  cones. 

Examples:    in    New    Mexico    and 
Arizona. 

5.  Faults  producing  step-like  terraces. 

6.  Chemical  or  organic  deposits,  such  as  marls  or  spring  deposits.  || 

*  A.  Winslow.    Science,  1893,  XXIII,  312. 

C.  F.  Marbut.    Am.  Geol.,  Feb.  1898,  XXI,  86-90. 

t  Geographical  development  of  alluvial  terraces.    By  R.  E.  Dodge.    Proc.  Boston  Soc. 

Nat.  Hist,,  1895,  XXVI,  257-273. 

Ohio  terraces.    Am.  Geol.,  1896,  XVIII,  227.  —  Russell.    Am.  Geol.,  Dec.  1898,  XXII,  362. 
H.  H.  Smith.    Brazil,  the  Amazon,  and  the  coast.    631-632.    New  York,  1897. 
I  Raised  shore-lines  on  Cape  Maysi,  Cuba.    By  O.  H.  Hershey.    Science,  Aug.  12,  1898, 

VIII,  179-180.  —  Hill.    Nat.  Geog.  Mag.,  IX,  242.  —  A.  Agassiz.    Nat.  Geog.  Mag., 

IX,  200,  208;  Bui.  Mus.  Comp.  Zool.,  XXVI,  4-5,  109-113,  116-117,  120,  130.  Cambridge, 
1894. 

The  topographic  features  of  lake  shores.    By  G.  K.  Gilbert.    5th  ann.  rep.  U.  S.  Geol. 

Surv.,  69-123.    Washington,  1885. 
\  Shaler.     Am.  Jour.  Sci.,  Mar.  1887,  p.  210. 
Gulliver.    Bui.  Geol.  Soc.  Am.,  Jan.  1900,  X,  492-495. 
|  The  origin  of  travertine  falls.    Science,  Aug.  2,  1901,  XIV,  181-185. 


with  the 

ing  the  soft  and  avoid- 
the hard  ones. 


Fig.  109. — A  meandering  upland 

stream  cutting  homogeneous 

rocks  and  becoming  more 

and  more  crooked. 


355 


356  TOPOGRAPHY. 


ISLANDS. 


(] 


T-V    .       t-  (  When  the  sea  encroaches  on  the  land,  leaving 

I      resisting  points. 

,   !  „  <  Sediments  deposited  by  tides,  currents  and 

Islands  of  <  Construction     3       gtreams 

I  Emergence  Igneous;  orographic  movements. 

V  Submergence        Subsidence  leaves  isolated  peaks  as  islands. 


Effects  of  Topography  upon  Civilization.* 

Relations  of  topography  to  — 

1.  Political  boundaries. 

2.  Harbors  and  marine  industries. t 

3.  Location  of  cities  and  manufactures.* 

4.  Art. 

Scenery. § 

5.  Agriculture. 

6.  Literature.il 

TOPOGRAPHIC  MODELS  OR  RELIEF  MAPS. IT 
Uses. 

Methods  of  construction. 
Materials  of  the  originals. 
Materials  used  for  the  finished  map. 
The  question  of  the  vertical  scale. 

*  Nature  and  man  in  America.    By  N.  S.  Shaler.    New  York,  1891. 

t  The  geological  history  of  harbors.    By  N.  S.  Shaler.    13th  ann.  rep.  U.  S.  Geol.  Surv., 

part  II,  93-209.  Washington,  1893. 
1  McGee.  Am.  Jour.  Sci.,  1890,  CXL,  16. 
\  The  scenery  of  Switzerland  and  the  causes  to  which  it  is  due.  By  Sir  John  Lubbock. 

New  York,  1896.    Tauchnitz  edition,  Leipzig,  1897. 
The  scenery  of  England.    By  Lord  Avebury.    New  York,  1902. 
The  scenery  of  Scotland  viewed  in  connection  with  its  physical  geology.    By  A.  Geikie. 

London,  1865.    2d  ed.,  London  and  New  York,  1887.    3d  ed.,  London,  1901. 
Landscape  geology:  a  plea  for  the  study  of  geology  by  landscape  painters.    By  Hugh 

Miller.    Edinburg  and  London,  1891. 

The  scientific  study  of  scenery.    By  J.  E.  Marr.     London,  1900. 
I  Types  of  scenery  and  their  influence  on  literature.    By  Sir  Archibald  Geikie.    London, 

1898. 
H  Topographical  and  geological   modeling.    By  O.  B.  Hardin.    Trans.  Am.  Inst.  Min. 

Eng.,  X,  264-267. 
The  construction  of  maps  in  relief.    By  John  H.  and  E.  B.  Hardin.    Trans.  Am.  Inst. 

Min.  Eng.,  XVI,  279-301. 
Topographic  models.    By  Cosmos  Mendeleff.    Nat.  Geog.  Mag.,  I,  254-268.    Washington, 

Relief  maps.    By  Marcus  Baker.    Bui.  Phil.  Soc.  Wash.,  XII,  349-368.    Washington,  1894. 


357 


359 


360 


361 


362 


INDEX. 


INDEX. 


Abrasion,  40. 
Acid  rocks,  222. 
Acids,  effect  of,  114,  180. 
Acrogens,  age  of,  300. 
yEolian  rocks,  18. 
Age  of  the  earth,  324. 

of  faults,  268. 

of  topography,  344. 
Agencies,  10. 
Agriculture,    influence    of    glacia- 

tion  on,  104. 
Algge,  184,  196. 
Alkali,  26. 
Alkaline  lakes,  130. 
Alluvial  soils,  26. 
Alteration  of  rocks,  272-280. 
Alternation  of  rock  beds,  218. 
Amphibians,  age  of,  300. 
Andesite,  222. 
Animals,  distributed  by  wind,  14. 

hasten  rock  decay,  180. 

man's  influence  on,  206. 

rocks  made  by,  196. 
Anthracite,  186,  188. 
Anticlines,  254-256. 
Ants,  182. 

Aqueous  agencies,  36,  54. 
Archaean,  302. 
Arches,  natural,  122. 
Architecture  and  glaciation,  100, 

104. 

Arenaceous  deposits,  212. 
Argillaceous  deposits,  212. 
Aridity,  126. 
Artesian  wells,  286. 
Ashes,  volcanic,  144,  146. 


Asphaltum,  186. 

Atmospheric  agencies,  12,  20,  32. 

Axes  of  folds,  252. 

Bamboos  protect  land,  184. 
Banks,  submarine,  70. 
Bars,  52,  74. 
Basalt,  222-224. 
Basaltic  columns,  234. 
Base-level,  50,  346. 
Basic  rocks,  222. 
Beach  cusps,  72. 
Beaches,  70. 

barrier,  76. 
Bedded  deposits,  232. 
Bedding,  214. 
Belt  series,  304. 

Bench  and  bluff  topography,  338. 
Bitter  lakes,  130. 
Bituminous  coal,  188. 
Blow-holes,  58. 
Blowing  caves,  120. 
Borax  lakes,  130. 
Bore,  62. 

Boring  mollusks,  172,  182. 
"Bottle  rocks, "338. 
Boulder-clay,  94. 
Boulders,  glacial,  88,  92. 

of  decomposition,  22. 

origin  of,  40,  62. 
Breccia,  212. 
Bryozoa,  202. 

Building-stones,  302,  308,  310,  314. 
Buried  valleys,  174,  334. 
Buttes,  origin  of,  332,  338. 

Marysville,  152. 


363 


Calcareous  deposits,  animal,  196. 

deposits,  plant,  196. 
Cambrian,  304. 
Canons,  48. 
Carbon  dioxide  in  air,  192. 

in  wood,  coal,  etc.,  186. 
Carbonaceous  deposits,  184. 
Carbonic  acid  in  water,  114. 
Carboniferous,  308. 
Caves,  64,  118. 
Cenozoic  period,  316-318. 
Chalk,  202,  212. 
Change  of  level,  170;  see  Elevation. 

of  temperature,  20. 
Chemical  agencies,  114-134. 

deposition,  122. 

erosion,  114-122. 
Chert,  202. 
Chimney  rocks,  338. 
Cinders,  volcanic,  44,  212,  224. 
Circumdenudation,  332,  338. 
Cities  buried,  210. 
Civilization  and  topography,  356. 
Clay,  boulder,  94. 

carried  in  water,  40,  44. 

causing  landslips,  38. 

origin  of,  116,  134. 

potters',  316. 

same  as  slate,  212. 
Cleavage,  240. 
Cliff  dwellings,  120. 
Climate,  32,  56. 
Coal,  anthracite,  186,  188. 

area  of,  190. 

bituminous,  186,  188. 

measures,  310. 

origin  of,  192. 
Column,  geologic,  300. 
Concentric  staining,  246. 
Concretions,  242. 
Cone-in-cone,  246. 
Conformity,  216. 
Conglomerate,  178. 
Consequent  streams,  352. 
Constructive  work  of  seas,  68. 

agents,  184,  196,  334. 


Contact  metamorphism,  274. 

Cooling  of  eruptives,  148,  220,  222. 

Copper  in  drift,  98. 

Coquina,  202. 

Coral  reef,  fossil,  200. 

reefs,  196-202. 
Corals,  174. 
Corrasion,  42. 
Correlation,  296. 
Country  rock,  234. 
Cracks,  226-228. 
Crater  lake,  352. 
Craters,  142. 
Creep,  256. 
Cretaceous,  314. 
Crevasses,  86. 
Crevices,  226-228. 
Crystallization,  274. 
Currents,  ocean,  56. 

stream,  44. 

tidal,  68. 

transporting  power,  44. 
Cusps,  72. 
"Cut-offs,  "40. 
Cuyahoga,  98. 
Cycle,  geographic,  354. 

Data  of  geology,  6. 
Date  of  glaciation,  106. 
Death  Gulch,  142. 
Decay  of  rocks,  22,  116. 
Decomposition,  boulders  of,  22. 
Deformation,  336. 
Dehydration,  280. 
Deltas,  52,  76. 
Deluge,  168. 
Denudation,  38,  50. 
Deposition,  chemical,  122. 

by  glaciers,  90. 

by  streams,  50. 

by  wind,  16. 

in  seas,  68. 

rate  of,  324. 
Deposits,  calcareous,  196. 

by  man,  210. 

carbonaceous,  184. 


364 


INDEX. 


Deposits,  ferruginous,  194. 

nitrogenous,  194. 

organic,  184. 

phosphatic,  204. 

plant,  184. 

siliceous,  194. 

spring,  122. 

sulphurous,  194. 
Depression,  174,  248. 
Depth  of  borings,  138. 

of  seas,  54. 
Devonian,  308. 
Diamonds,  192. 
Diatoms,  194. 
Dikes,  152,  224. 

sandstone,  238. 
Dip,  256. 

Discharge  of  streams,  46. 
Disintegration,  20-24. 
Displacement  of  rocks,  248,  266. 
Distribution  of  plants,  14. 

of  animals,  14. 

of  volcanoes,  150. 
Dolomitization,  280. 
Dormant  volcanoes,  152. 
Drainage,  affected   by  glaciation, 
102. 

primitive,  344. 
Drift,  86,  92. 
Driftless  area,  94. 
Drift-timber,  192. 
Dunes,  16,  210. 

checked,  184. 
Dust-storms,  12. 
Dynamical  geology,  10. 

Earth,  interior  of,  136. 

pillars,  34. 

Earthquakes,  162-170. 
Efflorescence,  26-30 
Elevation  and  temperature,  82. 

and  depression,  170. 

evidences  of,  170-174. 
Emergent  forms,  248-334. 
Enchanted  mesa,  338. 
Eocene,  316. 


Epicentrum,  164. 
Erosion,  chemical,  116. 

general,  38. 

glacial,  90. 

rate  of,  46,  324. 

stream,  38. 

valleys  of,  346. 

wave,  66. 

wind,  14. 
Erratics,  88,  92. 
Eruptions,  volcanic,  140. 
Eruptive  rocks,  see  Igneous. 
Evaporation,  26. 
Exfoliation,  22,  246. 
Expansion  of  rocks,  22. 
Extermination,  208. 
Extinct  volcanoes,  152. 

False  bedding,  216. 
Faults,  178,  262-271. 

by  earthquakes,  166. 

normal,  262. 

reversed,  264. 

shear,  266. 

valleys  formed  by,  346. 
Faunas,  influence  of  glaciation  on, 
102. 

influence  of  oceans  on,  56,  330. 
Feldspar,  116. 
Ferruginous  deposits,  194. 
"  Finger  lakes,"  104. 
Fishes,  age  of,  300. 
Fissures  by  earthquakes,  166. 
Fjords,  176. 

Flagstone  cleavage,  240. 
Flint,  202. 
Floating  stones,  46. 
Flocculation,  78. 
Floe-ice,  112. 
Flood-plains,  50. 
Flow,  laws  of,  44. 
Focus  of  earthquake,  164. 
Folds,  248,  252. 

forming  valleys,  346. 
Footprints,  218. 
Foot-wall,  234. 


INDEX. 


365 


Foraminifera,  202. 

Forests,  man's  influence  on,  206. 

protection  by,  184. 
Fossils,  defined,  292. 

uses  of,  292. 
Freezing,  24. 
Fret-work,  26-28. 
Frost,  24. 
Fulgurite,  246. 
Fusion  of  rocks,  138. 

Gangue,  234. 
Gas,  306,  308. 

volcanic,  142,  144. 
Geodes,  226,  242. 
Geologic  column,  300. 
Geology,  6. 
Geysers,  158-162. 
Glacial  epoch,  94-110. 

epoch,  causes,  108,  110. 

epoch,  date  of,  106. 

soils,  104. 

streams,  90. 

Glaciation  in  North  America,  94, 
104. 

influence  of,  100-104. 
Glaciers,  82-112. 

advance  and  retreat  of,  92. 

erosion  by,  90. 

movements  of,  84. 

origin  of,  82. 

theories  of,  106. 

work  of,  90. 
Gletscher-milch,  90. 
Gneiss,  222. 
Gold,  placer,  234. 
Gorges,  48. 
Grand  cafion,  48. 
Granites,  222,  302. 
Graphite,  192,  302. 
Gravel,  212. 
Gravity  faults,  262. 
Guano,  204. 
Gulf  stream,  32,  56. 
Gullies,  40. 
Gypsum  and  salt,  origin  of,  128. 


Gypsum,  bedded,  232. 
cleavage,  240. 
occurrence  of,  308,  312. 

Hail,  34. 

Hanging-wall,  234. 
Harbors,  74,  334. 
Hardening  of  rocks,  218. 
Hills,  anticlinal,  synclinal,  262. 
Historical  geology,  290. 
Hog-wallows,  20. 
Horse,  234. 
Hot  springs,  162. 

springs  deposits,  162. 

waters,  132. 
Human  records,  174. 

relics,  320. 
Humic  acids,  114. 
Hydration,  280. 

Ice,  82-112. 
Icebergs,  112. 

theory,  106. 
Ice-cap,  96. 
Ice  caves,  120. 
Igneous  agencies,  136. 

rocks,  156,  220. 
Inclusions,  144. 
Insects,  burrowing,  182. 

distributed,  208. 
Interior  of  the  earth,  136-140. 
Intrusions,  222. 
Invertebrates,  age  of,  300. 
Iron  ores,  302,  310,  318. 
"Iron  pots,"  242. 
Iron-sands,  226. 
Islands,  356. 
Isoclinal  ridges,  262-264. 
Isostacy,  248,  328. 

Jasper,  198,  212. 
Joints,  168,  234,  340. 
Jura  mountains,  94,  314. 
Jurassic,  314. 

Kaolin,  116,  134. 
Kettle-holes,  92. 


366 


INDEX. 


Laccolites,  154,  224. 
Laccolitic  mountains,  334. 
Lakes,  52,  350. 

alkaline,  130. 

aqueous  agencies  in,  52-54. 

bitter,  130. 

borax,  130. 

fresh-water,  52. 

geologic  work  of,  52. 

postglacial,  104. 

salt,  124-130. 
Laminae,  216. 
Landslides,  36,  168. 
Lapilli,  144. 
Lava,  148. 

ancient,  152. 

caves  in,  120. 

cones,  146. 

sheets,  222. 
Lead,  306. 

Lenticular  beds,  21f>. 
Levees,  natural,  50. 
Lignite,  composition  of,  186. 

changes  of,  188. 

occurrence,  318. 

origin  of,  188. 
Limestone,  caves  in,  118. 

changes  of,  212. 

origin  of,  202. 

Lithodomus  holes,  172,  182. 
Lobate  glaciers,  98. 
Local  metamorphism,  274. 
Lode,  226. 
Loess,  104. 

puppets,  242. 
Lower  Silurian,  304. 

Major  relief,  328. 

Mammals,  age  of,  300. 

Man  as  a  geologic  agent,  204. 

Manganese  polish,   see   Chemical 

Deposition. 
Man,  primitive,  320. 

epoch  of,  300. 

and  the  glacial  epoch,  108. 

influence  on  animals,  206. 


Man's  influence  on  forests,  206. 

plants,  204. 

land,  208. 

Mangroves  protect  land,  184. 
Marble,  occurrence,  302,  306. 

origin  of,  212. 
Marl,  196. 
Marmarosis,  274. 
Mechanical  aqueous  agencies,  36- 

80. 

Mesozoic,  312-316. 
Metamorphism,  272-278. 

local  or  contact,  274. 

regional,  276. 
Mineral  veins,  224-234. 
Mining,  influence  of  glaciation  on, 
104. 

placer,  234. 

risks  of,  232. 
Minor  relief,  332. 
Miocene,  316. 
Models,  356. 

Mollusks,  boring,  172,  182. 
Monocline,  256. 
Moraines,  86,  92. 
Mountain  chains,  332. 

laccolitic,  334. 
Mountains,  330. 

of  circumdenudation,  332. 
Mud  streams,  see  Landslips. 
Mud  volcanoes,  150. 

Needle-ice,  24. 
Niagara,  102,  106. 
Nitric  acid  in  rain,  114. 
Nitrogenous  deposits,  194. 
Normal  faults,  262. 

Obsidian,  148. 
Ocean  basins,  330. 

currents,  32. 

effects  of,  56. 

depth,  54. 

temperatures,  54. 
Oceans,  mechanical  work  of,  54. 
Oil,  origin  of,  186. 


367 


Oil,  occurrence  of,  306,  308. 

Psychozoic  period,  318. 

Oolites,  246. 

"  Pulpit  rocks,"  338. 

Ooze,  212. 

Pumice,  144. 

Orbicular  granite,  246. 

Ordovician,  304. 

Quartzite,  212. 

Ores,  origin  of,  226-230. 

Quaternary,  318. 

Organic  acids,  114. 

agencies,  180-204. 

Rain,  36. 

Outcrop,  252. 

Rain-prints,  218. 

Overloading,  52. 

Red  Sea,  126. 

Overturn,  258-262. 

Reefs,  coral,  196-202. 

"  Ox-bows,"  40,  50. 

stone,  124,  220. 

Oxygen  in  wood  and  coal,  186. 

Regelation  theory,  86. 

Regional  metamorphism,  276. 

Paleontology,  290-322. 

Relief,  topographic,  328. 

Paleozoic  period,  304-312. 

maps,  356. 

Peaks,  volcanic,  144. 

Replacement,  280. 

isolated,  330. 

Reptiles,  age  of,  300. 

Peat,  186. 

Residuary  products,  134. 

Peat-bog,  bursting  of,  186. 

soils,  24. 

Pebbles,  40,  42. 

Retreat  of  ice,  98. 

Peneplain,  50,  346. 

Reversed  faults,  264. 

Permian,  312. 

Ripple-marks,  216. 

Petrified  wood,  194. 

Rivers,  352. 

Petroleum,  186,  306,  308. 

Roads,  relation  to  glaciation,  104. 

Pholad  borings,  172,  182. 

Roches  moutonn6es,  92. 

Phospbate  deposits,  204. 

Roots  of  plants,  180. 

Physiography,  328-356. 

Pisolites,  246. 

Saddle  reefs,  248. 

Placer  deposits,  234. 

St.  Anthony's  falls,  106. 

Plants  distributed  by  wind,  14. 

Salt,  128. 

man's  influence  upon,  204. 

lakes,  124. 

hasten  rock  decay,  180. 

occurrence  of,  308,  310. 

preservative  work  of,  184. 

Salton  lake,  128. 

Plant  deposits,  184. 

Sand  grains,  44. 

Pleistocene,  318. 

grains,  abrasion  by,  14,  40. 

glaciation,  94. 

Sand-dunes,  16. 

Pliocene,  300,  316. 

Sandstone,  212. 

Plutonic  rocks,  222. 

seolian,  18,  212. 

Polishing  by  ice,  88. 

dikes,  238. 

Pororoca,  see  Bore. 

reefs,  124,  220. 

Porosity  of  rocks,  282. 

Sand-storms,  12. 

Pot-holes,  40,  42,  104. 

Scenery,  356. 

Primitive  man,  320. 

Schistosity,  240. 

Protective  agents,  184. 

Schists,  278. 

Pseudomorphs,  280. 

Sea-caves,  64. 

INDEX. 


Seas  and  oceans,  54-80. 

mechanical  work  of,  58. 
Sea-urchins,  180. 
Sedimentary  rocks,  212-220. 
Sediments,  50,  70. 
Seismograph,  166. 
Seismology,  162. 
Serpulje,  202. 
Shale,  212. 
Shear  faults,  266. 
Shingle,  212. 
Shore  forms,  66. 
Shrinkage,  226. 
Siliceous  deposits  by  animals,  202. 

deposits  by  plants,  194. 
Silicified  wood,  194. 
Silurian,  306. 
Sink-holes,  120. 
Slate,  212. 
Slaty  cleavage,  240. 
Slickensides,  268. 
Snow,  82. 
Snow-line,  82. 
Soda, 130. 
Soil,  cultivation  by  man,  210. 

from  volcanic  rocks,  156. 

glacial,  104. 

origin  of,  24. 
Solution,  chemical,  114. 
Sounds  by  earthquakes,  166. 
South  American  glaciation,  106. 
Spheroidal  weathering,  22. 
Spits,  52,  74. 
Sponges,  184,  202. 
Spray,  62. 
Springs,  282. 

deposits,  122. 

hot,  162. 
Stalactites,  122. 
Stalagmites,  122. 
Stone  reefs,  124,  220. 
Storm  beaches,  72. 
Stratified  rocks,  212. 
Stratum,  defined,  214. 
Streams  and  their  changes,  352. 

glacial,  90. 


Streams,  matter  in,  46. 

work  of,  38. 
Striae,  88. 
Strike,  256. 
Structural  features,  234. 

geology,  212-288. 
Stumps,  174;  see  Wood. 
Stylolite,  246. 
Subaqueous  forms,  334. 
Subaerial  forms,  334. 
Subglacial  streams,  90. 
Subjective  phenomena,  8. 
Submarine  banks,  76. 

volcanoes,  148. 
Submerged  valleys,  174. 
Subsidence  of  coral  reefs,  174. 
Sulphurous  deposits,  194. 
Sun-cracks,  218. 
Syncline,  254-256. 

Table  rocks,  338. 

Talus,  26. 

Temperature,  changes  of,  20. 

effect  of  changes,  20-24,  34. 

decreases  with  elevation,  82. 

increases  downward,  138. 

of  seas,  54. 
Tepee  buttes,  338. 
Terraces,  354. 
Tertiary,  316. 
Text-books,  4. 
Thickness  of  glacial  ice,  98. 

of  sediments,  176. 
Thrust  faults,  264. 
Tidal  waves,  62. 
Tides,  56. 

effect  of  wind  on,  56. 
Till,  94. 

Tilting  of  rocks,  252. 
Timber,  drift-,  192. 
Time,  geologic,  324. 
Tin,  234. 

Topographic  geology,  262,  328-356. 
Topography  and  glaciation,  102. 

and  civilization,  356. 
Trachyte,  222. 


INDEX. 


Transportation,  laws  of,  44. 

by  glaciers,  90. 

by  seas  and  ocean,  68. 

by  streams,  44. 

by  wind,  12. 

marine,  68. 
Trap,  222. 
Travertine,  122. 
Trenton  gravels,  108. 
Trenton  rocks,  300,  306. 
Triassic,  312. 
Tripolite,  194. 
Tufa,  122. 
Tuff,  154,  224. 
Tumbleweed,  14. 

Unconformity,  21(5. 
Underground  waters,  282. 
Undertow,  68. 
UnionidEe,  102. 
Unstratified  rocks,  220. 

Valleys,  48,  346. 

Vegetation,  influence  of  glaciation 

on,  102. 
Veins,  224. 

Velocity  and  transportation,  44. 
Volcanic  ashes,  12,  144. 

eruptions,  140. 

gases,  142. 

rocks,  148. 
Volcanoes,  140-156. 

active,  140. 

distribution  of,  150. 


Volcanoes,  dormant,  152. 
mud,  150. 
submarine,  148. 

Wabash  drainage,  102. 
Water,  32,  36. 

and  life,  34. 

solvent  power,  114. 

transporting  power,  44. 

underground,  132. 
Waterfalls,  origin  of,  48. 

recession  of,  324.  , 

Water-hyacinth,  184. 
Water-level  affected  by  wind,  30. 
Waves,  30,  58,  68. 

earthquake,  168. 

extraordinary,  62. 

tidal,  68. 

work  of,  58. 
Wearing  by  wind,  14. 
Weathering,  280. 
Wells,  286. 

artesian,  286. 

Wind,  effect  on  water-level,  30. 
effect  on  ocean  currents,  32. 
transporting  by,  12. 
wearing  by,  14. 
bedding,  18. 
Wood,  petrified,  194. 
Worms,  182. 
Wrinkles,  252. 

Yosemite  Valley,  100. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


NOV  2  3 
NOV  7     1958 

JUN  4     1965 


Form  L9-100m-9,'52(A3105)444 


The  RAFPH  D.  RKED  LIBRARY 


UC  SOUTHERN  REGIONAL  LIBRARY 


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